csu3_am335x/EVSE/GPL/mosquitto-2.0.13/man/mosquitto.conf.5.xml

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<refentry xml:id="mosquitto.conf" xmlns:xlink="http://www.w3.org/1999/xlink">
	<refmeta>
		<refentrytitle>mosquitto.conf</refentrytitle>
		<manvolnum>5</manvolnum>
		<refmiscinfo class="source">Mosquitto Project</refmiscinfo>
		<refmiscinfo class="manual">File formats and conventions</refmiscinfo>
	</refmeta>

	<refnamediv>
		<refname>mosquitto.conf</refname>
		<refpurpose>the configuration file for mosquitto</refpurpose>
	</refnamediv>

	<refsynopsisdiv>
		<cmdsynopsis>
			<command>mosquitto.conf</command>
		</cmdsynopsis>
	</refsynopsisdiv>

	<refsect1>
		<title>Description</title>
		<para><command>mosquitto.conf</command> is the configuration file for
		mosquitto. This file can reside anywhere as long as mosquitto can read
		it. By default, mosquitto does not need a configuration file and will
		use the default values listed below. See
		<citerefentry><refentrytitle><link xlink:href="mosquitto-8.html">mosquitto</link></refentrytitle><manvolnum>8</manvolnum></citerefentry>
		for information on how to load a configuration file.</para>
		<para>
			Mosquitto can be instructed to reload the configuration file by sending
			a SIGHUP signal as described in the Signals section of
			<citerefentry><refentrytitle><link xlink:href="mosquitto-8.html">mosquitto</link></refentrytitle><manvolnum>8</manvolnum></citerefentry>.
			Not all configuration options can be reloaded, as detailed in the options below.
		</para>
	</refsect1>

	<refsect1>
		<title>File Format</title>
		<para>All lines with a # as the very first character are treated as a
		comment.</para>
		<para>Configuration lines start with a variable name. The variable
		value is separated from the name by a single space.</para>
	</refsect1>

	<refsect1>
		<title>Authentication</title>
		<para>The authentication options described below allow a wide range of
			possibilities in conjunction with the listener options. This
			section aims to clarify the possibilities. An overview is also available at
			<ulink url="https://mosquitto.org/documentation/authentication-methods/"/></para>
		<para>The simplest option is to have no authentication at all. This is
			the default if no other options are given. Unauthenticated
			encrypted support is provided by using the certificate based
			SSL/TLS based options certfile and keyfile.</para>
		<para>MQTT provides username/password authentication as part of the
			protocol. Use the password_file option to define the valid
			usernames and passwords. Be sure to use network encryption if you
			are using this option otherwise the username and password will be
			vulnerable to interception. Use the
			<option>per_listener_settings</option> to control whether passwords
			are required globally or on a per-listener basis.</para>
		<para>Mosquitto provides the Dynamic Security plugin which handles
			username/password authentication and access control in a much
			more flexible way than a password file. See
			<ulink url="https://mosquitto.org/documentation/dynamic-security/"/>
			</para>
		<para>When using certificate based encryption there are three options
			that affect authentication. The first is require_certificate, which
			may be set to true or false. If false, the SSL/TLS component of the
			client will verify the server but there is no requirement for the
			client to provide anything for the server: authentication is
			limited to the MQTT built in username/password. If
			require_certificate is true, the client must provide a valid
			certificate in order to connect successfully. In this case, the
			second and third options, use_identity_as_username and
			use_subject_as_username, become relevant. If set to true,
			use_identity_as_username causes the Common Name (CN) from the
			client certificate to be used instead of the MQTT username for
			access control purposes. The password is not used because it is
			assumed that only authenticated clients have valid certificates.
			This means that any CA certificates you include in cafile or capath
			will be able to issue client certificates that are valid for
			connecting to your broker. If use_identity_as_username is false,
			the client must authenticate as normal (if required by
			password_file) through the MQTT options. The same principle applies
			for the use_subject_as_username option, but the entire certificate
			subject is used as the username instead of just the CN.</para>
		<para>When using pre-shared-key based encryption through the psk_hint
			and psk_file options, the client must provide a valid identity and
			key in order to connect to the broker before any MQTT communication
			takes place. If use_identity_as_username is true, the PSK identity
			is used instead of the MQTT username for access control purposes.
			If use_identity_as_username is false, the client may still
			authenticate using the MQTT username/password if using the
			password_file option.</para>
		<para>Both certificate and PSK based encryption are configured on a
			per-listener basis.</para>
		<para>Authentication plugins can be created to augment the
			password_file, acl_file and psk_file options with e.g. SQL based
			lookups.</para>
		<para>It is possible to support multiple authentication schemes at
			once. A config could be created that had a listener for all of the
			different encryption options described above and hence a large
			number of ways of authenticating.</para>
	</refsect1>

	<refsect1>
		<title>General Options</title>
		<variablelist>
			<varlistentry>
				<term><option>acl_file</option> <replaceable>file path</replaceable></term>
				<listitem>
					<para>Set the path to an access control list file. If
						defined, the contents of the file are used to control
						client access to topics on the broker.</para>
					<para>If this parameter is defined then only the topics
						listed will have access. Topic access is added with
						lines of the format:</para>

					<para><code>topic [read|write|readwrite|deny] &lt;topic&gt;</code></para>

					<para>The access type is controlled using "read", "write",
						"readwrite" or "deny". This parameter is optional (unless
						&lt;topic&gt; includes a space character) - if not
						given then the access is read/write.  &lt;topic&gt; can
						contain the + or # wildcards as in
						subscriptions. The "deny" option can used to explicitly
						deny access to a topic that would otherwise be granted
						by a broader read/write/readwrite statement. Any "deny"
						topics are handled before topics that grant read/write access.</para>

					<para>The first set of topics are applied to anonymous
						clients, assuming <option>allow_anonymous</option> is
						true. User specific topic ACLs are added after a user
						line as follows:</para>

					<para><code>user &lt;username&gt;</code></para>

					<para>The username referred to here is the same as in
						<option>password_file</option>. It is not the
						clientid.</para>

					<para>It is also possible to define ACLs based on pattern
						substitution within the topic. The form is the same as
						for the topic keyword, but using pattern as the
						keyword.</para>
					<para><code>pattern [read|write|readwrite|deny] &lt;topic&gt;</code></para>

					<para>The patterns available for substition are:</para>
					<itemizedlist mark="circle">
						<listitem><para>%c to match the client id of the client</para></listitem>
						<listitem><para>%u to match the username of the client</para></listitem>
					</itemizedlist>
					<para>The substitution pattern must be the only text for
						that level of hierarchy. Pattern ACLs apply to all
						users even if the "user" keyword has previously been
						given.</para>

					<para>Example:</para>
					<para><code>pattern write sensor/%u/data</code></para>
					<para>Allow access for bridge connection messages:</para>
					<para><code>pattern write $SYS/broker/connection/%c/state</code></para>

					<para>If the first character of a line of the ACL file is a
						# it is treated as a comment.</para>

					<para>If <option>per_listener_settings</option> is
						<replaceable>true</replaceable>, this option applies to
						the current listener being configured only. If
						<option>per_listener_settings</option> is
						<replaceable>false</replaceable>, this option applies
						to all listeners.</para>

					<para>Reloaded on reload signal. The currently loaded ACLs
						will be freed and reloaded. Existing subscriptions will
						be affected after the reload.</para>
					<para>See also
						<ulink url="https://mosquitto.org/documentation/dynamic-security/"/>
					</para>
				</listitem>
			</varlistentry>
			<varlistentry>
				<term><option>allow_anonymous</option> [ true | false ]</term>
				<listitem>
					<para>Boolean value that determines whether clients that
						connect without providing a username are allowed to
						connect. If set to <replaceable>false</replaceable>
						then another means of connection should be created to
						control authenticated client access.</para>
					<para>Defaults to <replaceable>false</replaceable>,
						unless no listeners are defined in the configuration
						file, in which case it set to <replaceable>true</replaceable>,
						but connections are only allowed from the local machine.</para>

					<para>If <option>per_listener_settings</option> is
						<replaceable>true</replaceable>, this option applies to
						the current listener being configured only. If
						<option>per_listener_settings</option> is
						<replaceable>false</replaceable>, this option applies
						to all listeners.</para>

					<important><para>In version 1.6.x and earlier, this option defaulted
						to <replaceable>true</replaceable> unless there was another security
						option set.</para></important>

					<para>Reloaded on reload signal.</para>
				</listitem>
			</varlistentry>
			<varlistentry>
				<term><option>allow_duplicate_messages</option> [ true | false ]</term>
				<listitem>
                    <para>This option is deprecated and will be removed in a
                        future version. The behaviour will default to true.
                    </para>
					<para>If a client is subscribed to multiple subscriptions
						that overlap, e.g. foo/# and foo/+/baz , then MQTT
						expects that when the broker receives a message on a
						topic that matches both subscriptions, such as
						foo/bar/baz, then the client should only receive the
						message once.</para>
					<para>Mosquitto keeps track of which clients a message has
						been sent to in order to meet this requirement. This
						option allows this behaviour to be disabled, which may
						be useful if you have a large number of clients
						subscribed to the same set of topics and want to
						minimise memory usage.</para>
					<para>It can be safely set to
						<replaceable>true</replaceable> if you know in advance
						that your clients will never have overlapping
						subscriptions, otherwise your clients must be able to
						correctly deal with duplicate messages even when then
						have QoS=2.</para>
					<para>Defaults to <replaceable>true</replaceable>.</para>

					<para>This option applies globally.</para>

					<para>Reloaded on reload signal.</para>
				</listitem>
			</varlistentry>
			<varlistentry>
				<term><option>allow_zero_length_clientid</option> [ true | false ]</term>
				<listitem>
					<para>MQTT 3.1.1 and MQTT 5 allow clients to connect with a zero
						length client id and have the broker generate a client
						id for them. Use this option to allow/disallow this
						behaviour. Defaults to true.</para>
					<para>See also the <option>auto_id_prefix</option> option.</para>

					<para>If <option>per_listener_settings</option> is
						<replaceable>true</replaceable>, this option applies to
						the current listener being configured only. If
						<option>per_listener_settings</option> is
						<replaceable>false</replaceable>, this option applies
						to all listeners.</para>

					<para>Reloaded on reload signal.</para>
				</listitem>
			</varlistentry>
			<varlistentry>
				<term><option>auth_plugin_deny_special_chars</option> [ true | false ]</term>
				<listitem>
					<para>If <replaceable>true</replaceable> then before an ACL
						check is made, the username/client id of the client
						needing the check is searched for the presence of
						either a '+' or '#' character. If either of these
						characters is found in either the username or client
						id, then the ACL check is denied before it is sent to
						the plugin.</para>
					<para>This check prevents the case where a malicious user
						could circumvent an ACL check by using one of these
						characters as their username or client id. This is the
						same issue as was reported with mosquitto itself as
						CVE-2017-7650.</para>
					<para>If you are entirely sure that the plugin you are
						using is not vulnerable to this attack (i.e. if you
						never use usernames or client ids in topics) then you
						can disable this extra check and hence have all ACL
						checks delivered to your plugin by setting this option
						to <replaceable>false</replaceable>.</para>
					<para>Defaults to <replaceable>true</replaceable>.</para>

					<para>Applies to the current authentication plugin being configured.</para>
					<para>Not currently reloaded on reload signal.</para>
				</listitem>
			</varlistentry>
			<varlistentry>
				<term><option>auto_id_prefix</option> <replaceable>prefix</replaceable></term>
				<listitem>
					<para>If <option>allow_zero_length_clientid</option> is
						<replaceable>true</replaceable>, this option allows you
						to set a string that will be prefixed to the
						automatically generated client ids to aid visibility in
						logs. Defaults to <option>auto-</option>.</para>

					<para>If <option>per_listener_settings</option> is
						<replaceable>true</replaceable>, this option applies to
						the current listener being configured only. If
						<option>per_listener_settings</option> is
						<replaceable>false</replaceable>, this option applies
						to all listeners.</para>

					<para>Reloaded on reload signal.</para>
				</listitem>
			</varlistentry>
			<varlistentry>
				<term><option>autosave_interval</option> <replaceable>seconds</replaceable></term>
				<listitem>
					<para>The number of seconds that mosquitto will wait
						between each time it saves the in-memory database to
						disk. If set to 0, the in-memory database will only be
						saved when mosquitto exits or when receiving the
						SIGUSR1 signal. Note that this setting only has an
						effect if persistence is enabled.  Defaults to 1800
						seconds (30 minutes).</para>

					<para>This option applies globally.</para>

					<para>Reloaded on reload signal.</para>
				</listitem>
			</varlistentry>
			<varlistentry>
				<term><option>autosave_on_changes</option> [ true | false ]</term>
				<listitem>
					<para>If <replaceable>true</replaceable>, mosquitto will
						count the number of subscription changes, retained
						messages received and queued messages and if the total
						exceeds <option>autosave_interval</option> then the
						in-memory database will be saved to disk. If
						<replaceable>false</replaceable>, mosquitto will save
						the in-memory database to disk by treating
						<option>autosave_interval</option> as a time in
						seconds.</para>

					<para>This option applies globally.</para>

					<para>Reloaded on reload signal.</para>
				</listitem>
			</varlistentry>
			<varlistentry>
				<term><option>check_retain_source</option> [ true | false ]</term>
				<listitem>
					<para>This option affects the scenario when a client
						subscribes to a topic that has retained messages. It is
						possible that the client that published the retained
						message to the topic had access at the time they
						published, but that access has been subsequently
						removed. If <option>check_retain_source</option> is set
						to true, the default, the source of a retained message
						will be checked for access rights before it is
						republished. When set to false, no check will be made
						and the retained message will always be
						published.</para>
					<para>This option applies globally, regardless of the
						<option>per_listener_settings</option> option.</para>
				</listitem>
			</varlistentry>
			<varlistentry>
				<term><option>clientid_prefixes</option> <replaceable>prefix</replaceable></term>
				<listitem>
                    <para>This option is deprecated and will be removed in a
                        future version.</para>
					<para>If defined, only clients that have a clientid with a
						prefix that matches clientid_prefixes will be allowed
						to connect to the broker. For example, setting
						"secure-" here would mean a client "secure-client"
						could connect but another with clientid "mqtt"
						couldn't. By default, all client ids are valid.</para>

					<para>This option applies globally.</para>

					<para>Reloaded on reload signal. Note that currently
						connected clients will be unaffected by any
						changes.</para>
				</listitem>
			</varlistentry>
			<varlistentry>
				<term><option>connection_messages</option> [ true | false ]</term>
				<listitem>
					<para>If set to <replaceable>true</replaceable>, the log
						will include entries when clients connect and
						disconnect. If set to <replaceable>false</replaceable>,
						these entries will not appear.</para>

					<para>This option applies globally.</para>

					<para>Reloaded on reload signal.</para>
				</listitem>
			</varlistentry>
			<varlistentry>
				<term><option>include_dir</option> <replaceable>dir</replaceable></term>
				<listitem>
					<para>External configuration files may be included by using
						the include_dir option. This defines a directory that
						will be searched for config files. All files that end
						in '.conf' will be loaded as a configuration file. It
						is best to have this as the last option in the main
						file. This option will only be processed from the main
						configuration file. The directory specified must not
						contain the main configuration file.</para>
					<para>The configuration files in
						<option>include_dir</option> are loaded in case
						sensitive alphabetical order, with the upper case of
						each letter ordered before the lower case of the same
						letter.</para>
						<example title="Load Order for include_dir" label="Load Order for include_dir">
							<para>Given the files
								<replaceable>b.conf</replaceable>,
								<replaceable>A.conf</replaceable>,
								<replaceable>01.conf</replaceable>,
								<replaceable>a.conf</replaceable>,
								<replaceable>B.conf</replaceable>, and
								<replaceable>00.conf</replaceable> inside
								<option>include_dir</option>, the config files
								would be loaded in this order:</para>
						<programlisting language="config">
00.conf
01.conf
A.conf
a.conf
B.conf
b.conf
</programlisting></example>
					<para>If this option is used multiple times, then each
						<option>include_dir</option> option is processed
						completely in the order that they are written in the
						main configuration file.</para>
						<example title="Load Order for Multiple include_dir" label="Load Order for Multiple include_dir">
							<para>Assuming a directory
								<replaceable>one.d</replaceable> containing
								files <replaceable>B.conf</replaceable> and
								<replaceable>C.conf</replaceable>, and a second
								directory <replaceable>two.d</replaceable>
								containing files
								<replaceable>A.conf</replaceable> and
								<replaceable>D.conf</replaceable>, and a
								config:</para>
						<programlisting language="config">
include_dir one.d
include_dir two.d
</programlisting><para>Then the config files would be loaded in this order:</para>
						<programlisting language="config">
# files from one.d
B.conf
C.conf
# files from two.d
A.conf
D.conf
</programlisting></example>
				</listitem>
			</varlistentry>
			<varlistentry>
				<term><option>log_dest</option> <replaceable>destinations</replaceable></term>
				<listitem>
					<para>Send log messages to a particular destination.
						Possible destinations are: <option>stdout</option>
						<option>stderr</option> <option>syslog</option>
						<option>topic</option> <option>file</option>
						<option>dlt</option>.</para>
					<para><option>stdout</option> and
						<option>stderr</option> log to the console on the
						named output.</para>
					<para><option>syslog</option> uses the userspace syslog
						facility which usually ends up in /var/log/messages or
						similar.</para>
					<para><option>topic</option> logs to the broker topic
						'$SYS/broker/log/&lt;severity&gt;', where severity is
						one of E, W, N, I, M which are error,
						warning, notice, information and message. Message type
						severity is used by the subscribe and unsubscribe
						log_type options and publishes log messages at
						$SYS/broker/log/M/subscribe and
						$SYS/broker/log/M/unsubscribe. Debug messages are never
						logged on topics.</para>
					<para>The <option>file</option> destination requires an
						additional parameter which is the file to be logged to,
						e.g. "log_dest file /var/log/mosquitto.log". The file
						will be closed and reopened when the broker receives a
						HUP signal. Only a single file destination may be
						configured.</para>
					<para>The <option>dlt</option> destination is for the
						automotive `Diagnostic Log and Trace` tool. This
						requires that Mosquitto has been compiled with DLT
						support.</para>
					<para>Use "log_dest none" if you wish to disable logging.
						Defaults to stderr. This option may be specified
						multiple times.</para>
					<para>Note that if the broker is running as a Windows
						service it will default to "log_dest none" and neither
						stdout nor stderr logging is available.</para>
					<para>Reloaded on reload signal.</para>
				</listitem>
			</varlistentry>
			<varlistentry>
				<term><option>log_facility</option> <replaceable>local facility</replaceable></term>
				<listitem>
					<para>If using syslog logging (not on Windows), messages
						will be logged to the "daemon" facility by default. Use
						the <option>log_facility</option> option to choose
						which of local0 to local7 to log to instead. The option
						value should be an integer value, e.g. "log_facility 5"
						to use local5.</para>
				</listitem>
			</varlistentry>
			<varlistentry>
				<term><option>log_timestamp</option> [ true | false ]</term>
				<listitem>
					<para>Boolean value, if set to
						<replaceable>true</replaceable> a timestamp value will
						be added to each log entry. The default is
						<replaceable>true</replaceable>.</para>
					<para>Reloaded on reload signal.</para>
				</listitem>
			</varlistentry>
			<varlistentry>
				<term><option>log_timestamp_format</option> <replaceable>format</replaceable></term>
				<listitem>
					<para>Set the format of the log timestamp. If left unset,
						this is the number of seconds since the Unix epoch.
						This option is a free text string which will be passed
						to the strftime function as the format specifier. To
						get an ISO 8601 datetime, for example:</para>
					<programlisting language="config">
log_timestamp_format %Y-%m-%dT%H:%M:%S
					</programlisting>
					<para>Reloaded on reload signal.</para>
				</listitem>
			</varlistentry>

			<varlistentry>
				<term><option>log_type</option> <replaceable>types</replaceable></term>
				<listitem>
					<para>Choose types of messages to log. Possible types are:
						<replaceable>debug</replaceable>,
						<replaceable>error</replaceable>,
						<replaceable>warning</replaceable>,
						<replaceable>notice</replaceable>,
						<replaceable>information</replaceable>,
						<replaceable>subscribe</replaceable>,
						<replaceable>unsubscribe</replaceable>,
						<replaceable>websockets</replaceable>,
						<replaceable>none</replaceable>,
						<replaceable>all</replaceable>.</para>
					<para>Defaults to <replaceable>error</replaceable>,
						<replaceable>warning</replaceable>, <replaceable>notice
						</replaceable>and
						<replaceable>information</replaceable>.  This option
						may be specified multiple times. Note that the
						<replaceable>debug </replaceable>type (used for
						decoding incoming/outgoing network packets) is never
						logged in topics.</para>
					<para>Reloaded on reload signal.</para>
				</listitem>
			</varlistentry>
			<varlistentry>
				<term><option>max_inflight_bytes</option> <replaceable>count</replaceable></term>
				<listitem>
					<para>Outgoing QoS 1 and 2 messages will be allowed in flight until this byte
						limit is reached. This allows control of outgoing message rate based on
						message size rather than message count. If the limit is set to 100,
						messages of over 100 bytes are still allowed, but only a single message
						can be in flight at once.  Defaults to 0. (No limit).</para>
					<para>See also the <option>max_inflight_messages</option> option.</para>

					<para>This option applies globally.</para>

					<para>Reloaded on reload signal.</para>
				</listitem>
			</varlistentry>
			<varlistentry>
				<term><option>max_inflight_messages</option> <replaceable>count</replaceable></term>
				<listitem>
					<para>The maximum number of outgoing QoS 1 or 2 messages that can be
						in the process of being transmitted simultaneously.
						This includes messages currently going through
						handshakes and messages that are being retried.
						Defaults to 20. Set to 0 for no maximum. If set to 1,
						this will guarantee in-order delivery of
						messages.</para>

					<para>This option applies globally.</para>

					<para>Reloaded on reload signal.</para>
				</listitem>
			</varlistentry>
			<varlistentry>
				<term><option>max_keepalive</option> <replaceable>value</replaceable></term>
				<listitem>
					<para>For MQTT v5 clients, it is possible to have the
						server send a "server keepalive" value that will
						override the keepalive value set by the client.  This
						is intended to be used as a mechanism to say that the
						server will disconnect the client earlier than it
						anticipated, and that the client should use the new
						keepalive value. The max_keepalive option allows you to
						specify that clients may only connect with keepalive
						less than or equal to this value, otherwise they will
						be sent a server keepalive telling them to use
						max_keepalive. This only applies to MQTT v5 clients.
						The maximum value allowable, and default value, is
						65535.</para>

					<para>
						Set to 0 to allow clients to set keepalive = 0, which
						means no keepalive checks are made and the client will
						never be disconnected by the broker if no messages are
						received. You should be very sure this is the behaviour
						that you want.
					</para>

					<para>
						For MQTT v3.1.1 and v3.1 clients, there is no mechanism
						to tell the client what keepalive value they should use.
						If an MQTT v3.1.1 or v3.1 client specifies a keepalive
						time greater than max_keepalive they will be sent a
						CONNACK message with the "identifier rejected" reason
						code, and disconnected.
					</para>

					<para>This option applies globally.</para>

					<para>Reloaded on reload signal.</para>
				</listitem>
			</varlistentry>
			<varlistentry>
				<term><option>max_packet_size</option> <replaceable>value</replaceable></term>
				<listitem>
					<para>For MQTT v5 clients, it is possible to have the
						server send a "maximum packet size" value that will
						instruct the client it will not accept MQTT packets
						with size greater than <option>value</option> bytes.
						This applies to the full MQTT packet, not just the
						payload. Setting this option to a positive value will
						set the maximum packet size to that number of bytes. If
						a client sends a packet which is larger than this
						value, it will be disconnected. This applies to all
						clients regardless of the protocol version they are
						using, but v3.1.1 and earlier clients will of course
						not have received the maximum packet size information.
						Defaults to no limit.</para>

					<para>This option applies to all clients, not just those
						using MQTT v5, but it is not possible to notify clients
						using MQTT v3.1.1 or MQTT v3.1 of the limit.</para>

					<para>Setting below 20 bytes is forbidden because it is
						likely to interfere with normal client operation even
						with small payloads.</para>

					<para>This option applies globally.</para>

					<para>Reloaded on reload signal.</para>
				</listitem>
			</varlistentry>
			<varlistentry>
				<term><option>max_queued_bytes</option> <replaceable>count</replaceable></term>
				<listitem>
					<para>The number of outgoing QoS 1 and 2 messages above those currently in-flight will be
						queued (per client) by the broker. Once this limit has been reached, subsequent
						messages will be silently dropped. This is an important option if you are sending
						messages at a high rate and/or have clients who are slow to respond or may be offline
						for extended periods of time.  Defaults to 0. (No maximum).</para>
					<para>See also the
						<option>max_queued_messages</option> option.
						If both max_queued_messages and max_queued_bytes are specified,
						packets will  be queued until the first limit is reached.
					</para>

					<para>This option applies globally.</para>

					<para>Reloaded on reload signal.</para>
				</listitem>
			</varlistentry>
			<varlistentry>
				<term><option>max_queued_messages</option> <replaceable>count</replaceable></term>
				<listitem>
					<para>The maximum number of QoS 1 or 2 messages to hold in the
						queue (per client) above those messages that are currently
						in flight. Defaults to 1000. Set to 0 for no maximum (not
						recommended). See also the
						<option>queue_qos0_messages</option> and
						<option>max_queued_bytes</option> options.</para>

					<para>This option applies globally.</para>

					<para>Reloaded on reload signal.</para>
				</listitem>
			</varlistentry>
			<varlistentry>
				<term><option>memory_limit</option> <replaceable>limit</replaceable></term>
				<listitem>
					<para>
						This option sets the maximum number of heap memory bytes that the broker
						will allocate, and hence sets a hard limit on memory use by the broker.
						Memory requests that exceed this value will be denied. The effect will
						vary depending on what has been denied. If an incoming message is being
						processed, then the message will be dropped and the publishing client
						will be disconnected. If an outgoing message is being sent, then the
						individual message will be dropped and the receiving client will be
						disconnected. Defaults to no limit.</para>
					<para>This option is only available if memory tracking support is compiled
						in.</para>
					<para>Reloaded on reload signal. Setting to a lower value and reloading will
						not result in memory being freed.</para>
				</listitem>
			</varlistentry>
			<varlistentry>
				<term><option>message_size_limit</option> <replaceable>limit</replaceable></term>
				<listitem>
					<para>This option sets the maximum publish payload size
						that the broker will allow. Received messages that
						exceed this size will not be accepted by the broker. This means that the
						message will not be forwarded on to subscribing clients, but the QoS flow
						will be completed for QoS 1 or QoS 2 messages. MQTT v5 clients using QoS 1
						or QoS 2 will receive a PUBACK or PUBREC with the "implementation specific
						error" reason code.</para>

					<para>The default value is 0, which means that all valid MQTT
						messages are accepted. MQTT imposes a maximum payload
						size of 268435455 bytes.</para>

					<para>This option applies globally.</para>

					<para>Reloaded on reload signal.</para>
				</listitem>
			</varlistentry>
			<varlistentry>
				<term><option>password_file</option> <replaceable>file path</replaceable></term>
				<listitem>
					<para>Set the path to a password file. If defined, the
						contents of the file are used to control client access
						to the broker. The file can be created using the
						<citerefentry><refentrytitle><link xlink:href="mosquitto_passwd-1.html">mosquitto_passwd</link></refentrytitle><manvolnum>1</manvolnum></citerefentry>
						utility. If mosquitto is compiled without TLS support
						(it is recommended that TLS support is included), then
						the password file should be a text file with each line
						in the format "username:password", where the colon and
						password are optional but recommended. If
						<option>allow_anonymous</option> is set to
						<replaceable>false</replaceable>, only users defined in
						this file will be able to connect. Setting
						<option>allow_anonymous</option> to
						<replaceable>true</replaceable> when
						<replaceable>password_file</replaceable>is defined is
						valid and could be used with acl_file to have e.g. read
						only guest/anonymous accounts and defined users that
						can publish.</para>

					<para>If <option>per_listener_settings</option> is
						<replaceable>true</replaceable>, this option applies to
						the current listener being configured only. If
						<option>per_listener_settings</option> is
						<replaceable>false</replaceable>, this option applies
						to all listeners.</para>

					<para>Reloaded on reload signal. The currently loaded
						username and password data will be freed and reloaded.
						Clients that are already connected will not be
						affected.</para>
					<para>See also
						<citerefentry><refentrytitle><link xlink:href="mosquitto_passwd-1.html">mosquitto_passwd</link></refentrytitle><manvolnum>1</manvolnum></citerefentry> and
						<ulink url="https://mosquitto.org/documentation/dynamic-security/"/>
					</para>
				</listitem>
			</varlistentry>
			<varlistentry>
				<term><option>per_listener_settings</option> [ true | false ]</term>
				<listitem>
					<para>If <replaceable>true</replaceable>, then
						authentication and access control settings will be
						controlled on a per-listener basis. The following
						options are affected:</para>
					<para><option>password_file</option>,
						<option>acl_file</option>, <option>psk_file</option>,
						<option>allow_anonymous</option>,
						<option>allow_zero_length_clientid</option>,
						<option>auto_id_prefix</option>.</para>
						<option>plugin</option>,
						<option>plugin_opt_*</option>,
					<para>Note that if set to true, then a durable client (i.e.
						with clean session set to false) that has disconnected
						will use the ACL settings defined for the listener that
						it was most recently connected to.</para>
					<para>The default behaviour is for this to be set to
						<replaceable>false</replaceable>, which maintains the
						settings behaviour from previous versions of
						mosquitto.</para>
					<para>Reloaded on reload signal.</para>
				</listitem>
			</varlistentry>
			<varlistentry>
				<term><option>persistence</option> [ true | false ]</term>
				<listitem>
					<para>If <replaceable>true</replaceable>, connection,
						subscription and message data will be written to the
						disk in mosquitto.db at the location dictated by
						persistence_location. When mosquitto is restarted, it
						will reload the information stored in mosquitto.db. The
						data will be written to disk when mosquitto closes and
						also at periodic intervals as defined by
						autosave_interval. Writing of the persistence database
						may also be forced by sending mosquitto the SIGUSR1
						signal. If <replaceable>false</replaceable>, the data
						will be stored in memory only. Defaults to
						<replaceable>false</replaceable>.</para>
					<para>The persistence file may change its format in a new
						version. The broker can currently read all old formats,
						but will only save in the latest format. It should always
						be safe to upgrade, but cautious users may wish to take a
						copy of the persistence file before installing a new
						version so that they can roll back to an earlier version
						if necessary.</para>

					<para>This option applies globally.</para>

					<para>Reloaded on reload signal.</para>
				</listitem>
			</varlistentry>
			<varlistentry>
				<term><option>persistence_file</option> <replaceable>file name</replaceable></term>
				<listitem>
					<para>The filename to use for the persistent database.
						Defaults to mosquitto.db.</para>

					<para>This option applies globally.</para>

					<para>Reloaded on reload signal.</para>
				</listitem>
			</varlistentry>
			<varlistentry>
				<term><option>persistence_location</option> <replaceable>path</replaceable></term>
				<listitem>
					<para>The path where the persistence database should be
						stored. If not given, then the current directory is used.</para>

					<para>This option applies globally.</para>

					<para>Reloaded on reload signal.</para>
				</listitem>
			</varlistentry>
			<varlistentry>
				<term><option>persistent_client_expiration</option> <replaceable>duration</replaceable></term>
				<listitem>
					<para>This option allows persistent clients (those with
						clean session set to false) to be removed if they do
						not reconnect within a certain time frame. This is a
						non-standard option. As far as the MQTT spec is
						concerned, persistent clients persist forever.</para>
					<para>Badly designed clients may set clean session to false
						whilst using a randomly generated client id. This leads
						to persistent clients that will never reconnect. This
						option allows these clients to be removed.</para>
					<para>The expiration period should be an integer followed
						by one of h d w m y for hour, day, week, month and year
						respectively. For example:</para>
					<itemizedlist mark="circle">
						<listitem><para>persistent_client_expiration 2m</para></listitem>
						<listitem><para>persistent_client_expiration 14d</para></listitem>
						<listitem><para>persistent_client_expiration 1y</para></listitem>
					</itemizedlist>
					<para>As this is a non-standard option, the default if not
						set is to never expire persistent clients.</para>

					<para>This option applies globally.</para>

					<para>Reloaded on reload signal.</para>
				</listitem>
			</varlistentry>
			<varlistentry>
				<term><option>pid_file</option> <replaceable>file path</replaceable></term>
				<listitem>
					<para>Write a pid file to the file specified. If not given
						(the default), no pid file will be written. If the pid
						file cannot be written, mosquitto will exit.</para>
					<para>If mosquitto is being automatically started by an
						init script it will usually be required to write a pid
						file. This should then be configured as e.g.
						/var/run/mosquitto/mosquitto.pid</para>
					<para>Not reloaded on reload signal.</para>
				</listitem>
			</varlistentry>
			<varlistentry>
				<term><option>plugin_opt_*</option> <replaceable>value</replaceable></term>
				<listitem>
					<para>
						Options to be passed to the most recent
						<option>plugin</option> defined in the
						configuration file. See the specific
						plugin instructions for details of what
						options are available.
					</para>

					<para>Applies to the current plugin being configured.</para>
					<para>
                        This is also available as the <option>auth_opt_*</option>
                        option, but this use is deprecated and will be removed
                        in a future version.
					</para>
				</listitem>
			</varlistentry>
			<varlistentry>
				<term><option>plugin</option> <replaceable>file path</replaceable></term>
				<listitem>
					<para>Specify an external module to use for authentication
						and access control. This allows custom
						username/password and access control functions to be
						created.</para>
					<para>Can be specified multiple times to load multiple
						plugins. The plugins will be processed in the order
						that they are specified.</para>
					<para>If <option>password_file</option>, or
						<option>acl_file</option> are used in the config file
						alongsize <option>plugin</option>, the plugin
						checks will run after the built in checks.</para>
					<para>Not currently reloaded on reload signal.</para>
					<para>See also
						<ulink url="https://mosquitto.org/documentation/dynamic-security/"/>
					</para>
					<para>
                        This is also available as the <option>auth_plugin</option>
                        option, but this use is deprecated and will be removed
                        in a future version.
					</para>
				</listitem>
			</varlistentry>
			<varlistentry>
				<term><option>psk_file</option> <replaceable>file path</replaceable></term>
				<listitem>
					<para>Set the path to a pre-shared-key file. This option
						requires a listener to be have PSK support enabled. If
						defined, the contents of the file are used to control
						client access to the broker. Each line should be in the
						format "identity:key", where the key is a hexadecimal
						string with no leading "0x". A client connecting to a
						listener that has PSK support enabled must provide a
						matching identity and PSK to allow the encrypted
						connection to proceed.</para>

					<para>If <option>per_listener_settings</option> is
						<replaceable>true</replaceable>, this option applies to
						the current listener being configured only. If
						<option>per_listener_settings</option> is
						<replaceable>false</replaceable>, this option applies
						to all listeners.</para>

					<para>Reloaded on reload signal. The currently loaded
						identity and key data will be freed and reloaded.
						Clients that are already connected will not be
						affected.</para>
				</listitem> </varlistentry>
			<varlistentry>
				<term><option>queue_qos0_messages</option> [ true | false ]</term>
				<listitem>
					<para>Set to <replaceable>true</replaceable> to queue
						messages with QoS 0 when a persistent client is
						disconnected. These messages are included in the limit
						imposed by max_queued_messages.  Defaults to
						<replaceable>false</replaceable>.</para>
					<para>Note that the MQTT v3.1.1 spec states that only QoS 1
						and 2 messages should be saved in this situation so
						this is a non-standard option.</para>

					<para>This option applies globally.</para>

					<para>Reloaded on reload signal.</para>
				</listitem>
			</varlistentry>
			<varlistentry>
				<term><option>retain_available</option> [ true | false ]</term>
				<listitem>
					<para>If set to false, then retained messages are not
						supported. Clients that send a message with the retain
						bit will be disconnected if this option is set to
						false. Defaults to true.</para>

					<para>This option applies globally.</para>

					<para>Reloaded on reload signal.</para>
				</listitem>
			</varlistentry>
			<varlistentry>
				<term><option>set_tcp_nodelay</option> [ true | false ]</term>
				<listitem>
					<para>If set to true, the TCP_NODELAY option will be set on
							client sockets to disable Nagle's algorithm. This
							has the effect of reducing latency of some messages
							at potentially increasing the number of TCP packets
							being sent. Defaults to false.</para>

					<para>This option applies globally.</para>

					<para>Reloaded on reload signal.</para>
				</listitem>
			</varlistentry>
			<varlistentry>
				<term><option>sys_interval</option> <replaceable>seconds</replaceable></term>
				<listitem>
					<para>The integer number of seconds between updates of the
						$SYS subscription hierarchy, which provides status
						information about the broker. If unset, defaults to 10
						seconds.</para>
					<para>Set to 0 to disable publishing the $SYS hierarchy
						completely.</para>

					<para>This option applies globally.</para>

					<para>Reloaded on reload signal.</para>
				</listitem>
			</varlistentry>
			<varlistentry>
				<term><option>upgrade_outgoing_qos</option> [ true | false ]</term>
				<listitem>
					<para>The MQTT specification requires that the QoS of a
						message delivered to a subscriber is never upgraded to
						match the QoS of the subscription. Enabling this option
						changes this behaviour. If
						<option>upgrade_outgoing_qos</option> is set
						<replaceable>true</replaceable>, messages sent to a
						subscriber will always match the QoS of its
						subscription. This is a non-standard option not
						provided for by the spec. Defaults to
						<replaceable>false</replaceable>.</para>

					<para>This option applies globally.</para>

					<para>Reloaded on reload signal.</para>
				</listitem>
			</varlistentry>
			<varlistentry>
				<term><option>user</option> <replaceable>username</replaceable></term>
				<listitem>
					<para>When run as root, change to this user and its primary
						group on startup. If set to "mosquitto" or left unset,
						and if the "mosquitto" user does not exist, then
						mosquitto will change to the "nobody" user instead.
						If this is set to another value and mosquitto is unable
						to change to this user and group, it will exit with an
						error. The user specified must have read/write access
						to the persistence database if it is to be written. If
						run as a non-root user, this setting has no effect.
						Defaults to mosquitto.</para>
					<para>This setting has no effect on Windows and so you
						should run mosquitto as the user you wish it to run
						as.</para>
					<para>Not reloaded on reload signal.</para>
				</listitem>
			</varlistentry>
		</variablelist>
	</refsect1>

	<refsect1>
		<title>Listeners</title>
		<para>The network ports that mosquitto listens on can be controlled
			using listeners. The default listener options can be overridden and
			further listeners can be created.</para>
		<refsect2>
			<title>General Options</title>
			<variablelist>
				<varlistentry>
					<term><option>bind_address</option> <replaceable>address</replaceable></term>
					<listitem>
                    <para>This option is deprecated and will be removed in a
						future version. Use the <option>listener</option> instead.
                    </para>
						<para>Listen for incoming network connections on the
							specified IP address/hostname only. This is useful
							to restrict access to certain network interfaces.
							To restrict access to mosquitto to the local host
							only, use "bind_address localhost". This only
							applies to the default listener. Use the
							<option>listener</option> option to control other
							listeners.</para>

						<para>It is recommended to use an explicit
							<option>listener</option> rather than rely on the
							implicit default listener options like this.</para>

						<para>Not reloaded on reload signal.</para>
					</listitem>
				</varlistentry>
				<varlistentry>
					<term><option>bind_interface</option> <replaceable>device</replaceable></term>
					<listitem>
						<para>Listen for incoming network connections only on
							the specified interface. This is similar to the
							<option>bind_address</option> option but is useful
							when an interface has multiple addresses or the
							address may change.</para>
						<para>If used at the same time as the
							<option>bind_address</option> for the default
							listener, or the <replaceable>bind
							address/host</replaceable> part of the
							<option>listener</option>, then <option>bind_interface</option>
							will take priority.</para>
						<para>This option is not available on Windows.</para>
						<para>Not reloaded on reload signal.</para>
					</listitem>
				</varlistentry>
				<varlistentry>
					<term><option>http_dir</option> <replaceable>directory</replaceable></term>
					<listitem>
						<para>When a listener is using the websockets protocol,
							it is possible to serve http data as well. Set
							<option>http_dir</option> to a directory which
							contains the files you wish to serve. If this
							option is not specified, then no normal http
							connections will be possible.</para>
						<para>Not reloaded on reload signal.</para>
					</listitem>
				</varlistentry>
				<varlistentry>
					<term><option>listener</option> <replaceable>port</replaceable> <replaceable><optional>bind address/host/unix socket path</optional></replaceable></term>
					<listitem>
						<para>Listen for incoming network connection on the
							specified port. A second optional argument allows
							the listener to be bound to a specific ip
							address/hostname. If this variable is used and
							neither the global <option>bind_address</option>
							nor <option>port</option> options are used then the
							default listener will not be started.</para>

						<para>The <option>bind address/host</option> option
							allows this listener to be bound to a specific IP
							address by passing an IP address or hostname. For
							websockets listeners, it is only possible to pass
							an IP address here.</para>

						<para>On systems that support Unix Domain Sockets, this
							option can also be used to create a Unix socket rather
							than opening a TCP socket. In this case, the port must
							be set to 0, and the unix socket path must be given.</para>

						<para>This option may be specified multiple times. See
							also the <option>mount_point</option>
							option.</para>
						<para>Not reloaded on reload signal.</para>
					</listitem>
				</varlistentry>
				<varlistentry>
					<term><option>max_connections</option> <replaceable>count</replaceable></term>
					<listitem>
						<para>Limit the total number of clients connected for
							the current listener. Set to <literal>-1</literal>
							to have "unlimited" connections. Note that other
							limits may be imposed that are outside the control
							of mosquitto.  See e.g.
							<citerefentry><refentrytitle><link xlink:href="http://linux.die.net/man/5/limits.conf">limits.conf</link></refentrytitle></citerefentry>.</para>
						<para>Not reloaded on reload signal.</para>
					</listitem>
				</varlistentry>
				<varlistentry>
					<term><option>max_qos</option> <replaceable>value</replaceable></term>
					<listitem>
						<para>Limit the QoS value allowed for clients connecting to this
							listener. Defaults to 2, which means any QoS can be
							used. Set to 0 or 1 to limit to those QoS values.
							This makes use of an MQTT v5 feature to notify
							clients of the limitation. MQTT v3.1.1 clients will
							not be aware of the limitation. Clients publishing
							to this listener with a too-high QoS will be
							disconnected.</para>
						<para>Not reloaded on reload signal.</para>
					</listitem>
				</varlistentry>
				<varlistentry>
					<term><option>max_topic_alias</option> <replaceable>number</replaceable></term>
					<listitem>
						<para>This option sets the maximum number topic aliases
							that an MQTT v5 client is allowed to create. This option
							applies per listener. Defaults to 10. Set to 0 to
							disallow topic aliases. The maximum value possible is 65535.</para>
						<para>Not reloaded on reload signal.</para>
					</listitem>
				</varlistentry>
				<varlistentry>
					<term><option>mount_point</option> <replaceable>topic prefix</replaceable></term>
					<listitem>
						<para>This option is used with the listener option to
							isolate groups of clients. When a client connects
							to a listener which uses this option, the string
							argument is attached to the start of all topics for
							this client. This prefix is removed when any
							messages are sent to the client.  This means a
							client connected to a listener with mount point
							<replaceable>example</replaceable> can only see
							messages that are published in the topic hierarchy
							<replaceable>example</replaceable> and below.</para>
						<para>Not reloaded on reload signal.</para>
					</listitem>
				</varlistentry>
				<varlistentry>
					<term><option>port</option> <replaceable>port number</replaceable></term>
					<listitem>
                    <para>This option is deprecated and will be removed in a
						future version. Use the <option>listener</option> instead.
                    </para>
						<para>Set the network port for the default listener to
							listen on. Defaults to 1883.</para>
						<para>Not reloaded on reload signal.</para>

						<para>It is recommended to use an explicit
							<option>listener</option> rather than rely on the
							implicit default listener options like this.</para>
					</listitem>
				</varlistentry>
				<varlistentry>
					<term><option>protocol</option> <replaceable>value</replaceable></term>
					<listitem>
						<para>Set the protocol to accept for the current listener. Can
							be <option>mqtt</option>, the default, or
							<option>websockets</option> if available.</para>
						<para>Websockets support is currently disabled by
							default at compile time. Certificate based TLS may be used
							with websockets, except that only the
							<option>cafile</option>, <option>certfile</option>,
							<option>keyfile</option>, <option>ciphers</option>, and
							<option>ciphers_tls1.3</option> options are
							supported.</para>
						<para>Not reloaded on reload signal.</para>
					</listitem>
				</varlistentry>
				<varlistentry>
					<term><option>socket_domain</option> [ ipv4 | ipv6 ]</term>
					<listitem>
						<para>By default, a listener will attempt to listen on
							all supported IP protocol versions. If you do not
							have an IPv4 or IPv6 interface you may wish to
							disable support for either of those protocol
							versions. In particular, note that due to the
							limitations of the websockets library, it will only
							ever attempt to open IPv6 sockets if IPv6 support
							is compiled in, and so will fail if IPv6 is not
							available.</para>
						<para>Set to <option>ipv4</option> to force the
							listener to only use IPv4, or set to
							<option>ipv6</option> to force the listener to only
							use IPv6. If you want support for both IPv4 and
							IPv6, then do not use the
							<option>socket_domain</option> option.</para>
						<para>Not reloaded on reload signal.</para>
					</listitem>
				</varlistentry>
				<varlistentry>
					<term><option>use_username_as_clientid</option> [ true | false ]</term>
					<listitem>
						<para>Set <option>use_username_as_clientid</option> to
							true to replace the clientid that a client
							connected with its username. This allows
							authentication to be tied to the clientid, which
							means that it is possible to prevent one client
							disconnecting another by using the same
							clientid. Defaults to false.</para>
						<para>If a client connects with no username it will be
							disconnected as not authorised when this option is
							set to true. Do not use in conjunction with
							<option>clientid_prefixes</option>.</para>
						<para>See also
							<option>use_identity_as_username</option>.</para>
						<para>Not reloaded on reload signal.</para>
					</listitem>
				</varlistentry>
				<varlistentry>
					<term><option>websockets_log_level</option> <replaceable>level</replaceable></term>
					<listitem>
						<para>Change the websockets logging level. This is a
							global option, it is not possible to set per
							listener. This is an integer that is interpreted by
							libwebsockets as a bit mask for its lws_log_levels
							enum. See the libwebsockets documentation for more
							details.</para>
						<para>To use this option, <option>log_type
								websockets</option> must also be enabled.
							Defaults to 0.</para>
					</listitem>
				</varlistentry>
				<varlistentry>
					<term><option>websockets_headers_size</option> <replaceable>size</replaceable></term>
					<listitem>
						<para>Change the websockets headers size. This is a
							global option, it is not possible to set per
							listener. This option sets the size of the buffer
							used in the libwebsockets library when reading HTTP
							headers. If you are passing large header data such
							as cookies then you may need to increase this
							value. If left unset, or set to 0, then the default
							of 1024 bytes will be used.</para>
					</listitem>
				</varlistentry>
			</variablelist>
		</refsect2>
		<refsect2>
			<title>Certificate based SSL/TLS Support</title>
			<para>The following options are available for all listeners to
				configure certificate based SSL support. See also
				"Pre-shared-key based SSL/TLS support".</para>
			<variablelist>
				<varlistentry>
					<term><option>cafile</option> <replaceable>file path</replaceable></term>
					<listitem>
						<para><option>cafile</option> is used to define the
							path to a file containing the PEM encoded CA
							certificates that are trusted when checking incoming
							client certificates.
						</para>
					</listitem>
				</varlistentry>
				<varlistentry>
					<term><option>capath</option> <replaceable>directory path</replaceable></term>
					<listitem>
						<para><option>capath</option> is used to define a
							directory that contains PEM encoded CA certificates
							that are trusted when checking incoming client
							certificates. For <option>capath</option> to
							work correctly, the certificates files must have
							".pem" as the file ending and you must run
							"openssl rehash &lt;path to capath&gt;" each time
							you add/remove a certificate.
						</para>
					</listitem>
				</varlistentry>
				<varlistentry>
					<term><option>certfile</option> <replaceable>file path</replaceable></term>
					<listitem>
						<para>
							Path to the PEM encoded server certificate. This
							option and <option>keyfile</option> must be present
							to enable certificate based TLS encryption.
						</para>
						<para>
							The certificate pointed to by this option will be
							reloaded when Mosquitto receives a SIGHUP signal.
							This can be used to load new certificates prior to
							the existing ones expiring.
						</para>
					</listitem>
				</varlistentry>
				<varlistentry>
					<term><option>ciphers</option> <replaceable>cipher:list</replaceable></term>
					<listitem>
                        <para>
                            The list of allowed ciphers for this listener, for
                            TLS v1.2 and earlier only, each separated with
                            a colon. Available ciphers can be obtained using
                            the "openssl ciphers" command.
                        </para>
					</listitem>
				</varlistentry>
				<varlistentry>
					<term><option>ciphers_tls1.3</option> <replaceable>cipher:list</replaceable></term>
					<listitem>
                        <para>
                            The list of allowed ciphersuites for this listener,
                            for TLS v1.3, each separated with a colon.
                        </para>
					</listitem>
				</varlistentry>
				<varlistentry>
					<term><option>crlfile</option> <replaceable>file path</replaceable></term>
					<listitem>
						<para>If you have <option>require_certificate</option>
							set to <replaceable>true</replaceable>, you can
							create a certificate revocation list file to revoke
							access to particular client certificates. If you
							have done this, use crlfile to point to the PEM
							encoded revocation file.</para>
					</listitem>
				</varlistentry>
				<varlistentry>
					<term><option>dhparamfile</option> <replaceable>file path</replaceable></term>
					<listitem>
						<para>To allow the use of ephemeral DH key exchange,
							which provides forward security, the listener must
							load DH parameters. This can be specified with the
							dhparamfile option. The dhparamfile can be
							generated with the command e.g.</para>
						<programlisting>
openssl dhparam -out dhparam.pem 2048</programlisting>
					</listitem>
				</varlistentry>
				<varlistentry>
					<term><option>keyfile</option> <replaceable>file path</replaceable></term>
					<listitem>
						<para>
							Path to the PEM encoded server key. This
							option and <option>certfile</option> must be present
							to enable certificate based TLS encryption.
						</para>
						<para>
							The private key pointed to by this option will be
							reloaded when Mosquitto receives a SIGHUP signal.
							This can be used to load new keys prior to
							the existing ones expiring.
						</para>
					</listitem>
				</varlistentry>
				<varlistentry>
					<term><option>require_certificate</option> [ true | false ]</term>
					<listitem>
						<para>By default an SSL/TLS enabled listener will
							operate in a similar fashion to a https enabled web
							server, in that the server has a certificate signed
							by a CA and the client will verify that it is a
							trusted certificate.  The overall aim is encryption
							of the network traffic.  By setting
							<option>require_certificate</option> to
							<replaceable>true</replaceable>, a client connecting
							to this listener must provide a valid certificate in
							order for the network connection to proceed. This
							allows access to the broker to be controlled outside
							of the mechanisms provided by MQTT.</para>
					</listitem>
				</varlistentry>
				<varlistentry>
					<term><option>tls_engine</option> <replaceable>engine</replaceable></term>
					<listitem>
						<para>A valid openssl engine id. These can be listed with
						openssl engine command.</para>
					</listitem>
				</varlistentry>
				<varlistentry>
					<term><option>tls_engine_kpass_sha1</option> <replaceable>engine_kpass_sha1</replaceable></term>
					<listitem>
						<para>SHA1 of the private key password when using an
							TLS engine.  Some TLS engines such as the TPM
							engine may require the use of a password in order
							to be accessed.  This option allows a hex encoded
							SHA1 hash of the password to the engine directly,
							instead of the user being prompted for the
							password.</para>
					</listitem>
				</varlistentry>
				<varlistentry>
					<term><option>tls_keyform</option> [ pem | engine ]</term>
					<listitem>
						<para>Specifies the type of private key in use when
							making TLS connections.. This can be "pem" or
							"engine". This parameter is useful when a TPM
							module is being used and the private key has been
							created with it. Defaults to "pem", which means
							normal private key files are used.</para>
					</listitem>
				</varlistentry>
				<varlistentry>
					<term><option>tls_version</option> <replaceable>version</replaceable></term>
					<listitem>
						<para>Configure the minimum version of the TLS protocol to be
							used for this listener. Possible values are
							<replaceable>tlsv1.3</replaceable>,
							<replaceable>tlsv1.2</replaceable> and
							<replaceable>tlsv1.1</replaceable>. If left unset,
							the default of allowing TLS v1.3 and v1.2.</para>
						<para>In Mosquitto version 1.6.x and earlier, this
							option set the only TLS protocol version that
							was allowed, rather than the minimum.</para>
					</listitem>
				</varlistentry>
				<varlistentry>
					<term><option>use_identity_as_username</option> [ true | false ]</term>
					<listitem>
						<para>If <option>require_certificate</option> is
							<replaceable>true</replaceable>, you may set
							<option>use_identity_as_username</option> to
							<replaceable>true</replaceable> to use the CN value
							from the client certificate as a username. If this
							is <replaceable>true</replaceable>, the
							<option>password_file</option> option will not be
							used for this listener.</para>
						<para>This takes priority over
							<option>use_subject_as_username</option> if both
							are set to <replaceable>true</replaceable>.</para>
						<para>See also
							<option>use_subject_as_username</option></para>
					</listitem>
				</varlistentry>
				<varlistentry>
					<term><option>use_subject_as_username</option> [ true | false ]</term>
					<listitem>
						<para>If <option>require_certificate</option> is
							<replaceable>true</replaceable>, you may set
							<option>use_subject_as_username</option> to
							<replaceable>true</replaceable> to use the complete subject value
							from the client certificate as a username. If this
							is <replaceable>true</replaceable>, the
							<option>password_file</option> option will not be
							used for this listener.</para>
						<para>The subject will be generated in a form similar
							to <option>CN=test client,OU=Production,O=Server,L=Nottingham,ST=Nottinghamshire,C=GB</option>.</para>
						<para>See also
							<option>use_identity_as_username</option></para>
					</listitem>
				</varlistentry>
			</variablelist>
		</refsect2>
		<refsect2>
			<title>Pre-shared-key based SSL/TLS Support</title>
			<para>The following options are available for all listeners to
				configure pre-shared-key based SSL support. See also
				"Certificate based SSL/TLS support".</para>
			<variablelist>
				<varlistentry>
					<term><option>ciphers</option> <replaceable>cipher:list</replaceable></term>
					<listitem>
						<para>When using PSK, the encryption ciphers used will
							be chosen from the list of available PSK ciphers.
							If you want to control which ciphers are available,
							use this option.  The list of available ciphers can
							be optained using the "openssl ciphers" command and
							should be provided in the same format as the output
							of that command.</para>
					</listitem>
				</varlistentry>
				<varlistentry>
					<term><option>psk_hint</option> <replaceable>hint</replaceable></term>
					<listitem>
						<para>The <option>psk_hint</option> option enables
							pre-shared-key support for this listener and also
							acts as an identifier for this listener. The hint
							is sent to clients and may be used locally to aid
							authentication. The hint is a free form string that
							doesn't have much meaning in itself, so feel free
							to be creative.</para>
						<para>If this option is provided, see
							<option>psk_file</option> to define the pre-shared
							keys to be used or create a security plugin to
							handle them.</para>
					</listitem>
				</varlistentry>
				<varlistentry>
					<term><option>tls_version</option> <replaceable>version</replaceable></term>
					<listitem>
						<para>Configure the minimum version of the TLS protocol to be
							used for this listener. Possible values are
							<replaceable>tlsv1.3</replaceable>,
							<replaceable>tlsv1.2</replaceable> and
							<replaceable>tlsv1.1</replaceable>. If left unset,
							the default of allowing TLS v1.3 and v1.2.</para>
						<para>In Mosquitto version 1.6.x and earlier, this
							option set the only TLS protocol version that
							was allowed, rather than the minimum.</para>
					</listitem>
				</varlistentry>
				<varlistentry>
					<term><option>use_identity_as_username</option> [ true | false ]</term>
					<listitem>
						<para>Set <option>use_identity_as_username</option> to
							have the psk identity sent by the client used as
							its username.  The username will be checked as
							normal, so <option>password_file</option> or
							another means of authentication checking must be
							used. No password will be used.</para>
					</listitem>
				</varlistentry>
			</variablelist>
		</refsect2>
	</refsect1>

	<refsect1>
		<title>Configuring Bridges</title>
		<para>Multiple bridges (connections to other brokers) can be configured
		using the following variables.</para>
		<para>Bridges cannot currently be reloaded on reload signal.</para>
		<variablelist>
			<varlistentry>
				<term><option>address</option> <replaceable>address[:port]</replaceable> <replaceable>[address[:port]]</replaceable></term>
				<term><option>addresses</option> <replaceable>address[:port]</replaceable> <replaceable>[address[:port]]</replaceable></term>
				<listitem>
					<para>Specify the address and optionally the port of the
						bridge to connect to. This must be given for each
						bridge connection. If the port is not specified, the
						default of 1883 is used.</para>
					<para>If you use an IPv6 address, then the port is not
						optional.</para>
					<para>Multiple host addresses can be specified on the
						address config. See the <option>round_robin</option>
						option for more details on the behaviour of bridges
						with multiple addresses.</para>
				</listitem>
			</varlistentry>
			<varlistentry>
				<term><option>bridge_attempt_unsubscribe</option> [ true | false ]</term>
				<listitem>
					<para>If a bridge has topics that have "out" direction, the
						default behaviour is to send an unsubscribe request to
						the remote broker on that topic. This means that
						changing a topic direction from "in" to "out" will not
						keep receiving incoming messages. Sending these
						unsubscribe requests is not always desirable, setting
						<option>bridge_attempt_unsubscribe</option> to
						<replaceable>false</replaceable> will disable sending
						the unsubscribe request. Defaults to
						<replaceable>true</replaceable>.</para>
				</listitem>
			</varlistentry>
			<varlistentry>
				<term><option>bridge_bind_address</option> <replaceable>ip address</replaceable></term>
				<listitem>
					<para>
						If you need to have the bridge connect over a particular
						network interface, use bridge_bind_address to tell the
						bridge which local IP address the socket should bind to,
						e.g. <option>bridge_bind_address 192.168.1.10</option>.
					</para>
				</listitem>
			</varlistentry>
			<varlistentry>
				<term><option>bridge_max_packet_size</option> <replaceable>value</replaceable></term>
				<listitem>
					<para>
						If you wish to restrict the size of messages sent to a
						remote bridge, use this option. This sets the maximum
						number of bytes for the total message, including headers
						and payload. Note that MQTT v5 brokers may provide their
						own maximum-packet-size property. In this case, the
						smaller of the two limits will be used. Set to 0 for
						"unlimited".
					</para>
				</listitem>
			</varlistentry>
			<varlistentry>
				<term><option>bridge_outgoing_retain</option> [ true | false ]</term>
				<listitem>
					<para>Some MQTT brokers do not allow retained messages. MQTT v5 gives
						a mechanism for brokers to tell clients that they do not support
						retained messages, but this is not possible for MQTT v3.1.1 or v3.1.
						If you need to bridge to a v3.1.1 or v3.1 broker that does not support
						retained messages, set the <option>bridge_outgoing_retain</option>
						option to <replaceable>false</replaceable>. This will remove the
						retain bit on all outgoing messages to that bridge, regardless of any
						other setting. Defaults to <replaceable>true</replaceable>.</para>
				</listitem>
			</varlistentry>

			<varlistentry>
				<term><option>bridge_protocol_version</option> <replaceable>version</replaceable></term>
				<listitem>
					<para>Set the version of the MQTT protocol to use with for
						this bridge. Can be one of
						<replaceable>mqttv50</replaceable>,
						<replaceable>mqttv311</replaceable> or
						<replaceable>mqttv31</replaceable>. Defaults to
						<replaceable>mqttv311</replaceable>.</para>
				</listitem>
			</varlistentry>
			<varlistentry>
				<term><option>cleansession</option> [ true | false ]</term>
				<listitem>
					<para>Set the clean session option for this bridge. Setting
						to <replaceable>false</replaceable> (the default),
						means that all subscriptions on the remote broker are
						kept in case of the network connection dropping. If set
						to <replaceable>true</replaceable>, all subscriptions
						and messages on the remote broker will be cleaned up if
						the connection drops. Note that setting to
						<replaceable>true</replaceable> may cause a large
						amount of retained messages to be sent each time the
						bridge reconnects.</para>
					<para>If you are using bridges with
						<option>cleansession</option> set to
						<replaceable>false</replaceable> (the default), then
						you may get unexpected behaviour from incoming topics
						if you change what topics you are subscribing to. This
						is because the remote broker keeps the subscription for
						the old topic.  If you have this problem, connect your
						bridge with <option>cleansession</option> set to
						<replaceable>true</replaceable>, then reconnect with
						cleansession set to <replaceable>false</replaceable> as
						normal.</para>
				</listitem>
			</varlistentry>
			<varlistentry>
				<term><option>local_cleansession</option> [ true | false]</term>
				<listitem>
					<para>The regular <option>cleansession</option> covers both the local subscriptions
					and the remote subscriptions.   local_cleansession allows splitting this.
					Setting <replaceable>false</replaceable> will mean that the local connection
					will preserve subscription, independent of the remote connection.
					</para>
					<para>Defaults to the value of bridge.cleansession unless explicitly specified.</para>
				</listitem>
			</varlistentry>
			<varlistentry>
				<term><option>connection</option> <replaceable>name</replaceable></term>
				<listitem>
					<para>This variable marks the start of a new bridge
						connection. It is also used to give the bridge a name
						which is used as the client id on the remote
						broker.</para>
				</listitem>
			</varlistentry>
			<varlistentry>
				<term><option>keepalive_interval</option> <replaceable>seconds</replaceable></term>
				<listitem>
					<para>Set the number of seconds after which the bridge
						should send a ping if no other traffic has occurred.
						Defaults to 60. A minimum value of 5 seconds
						is allowed.</para>
				</listitem>
			</varlistentry>
			<varlistentry>
				<term><option>idle_timeout</option> <replaceable>seconds</replaceable></term>
				<listitem>
					<para>Set the amount of time a bridge using the lazy start
						type must be idle before it will be stopped. Defaults
						to 60 seconds.</para>
				</listitem>
			</varlistentry>
			<varlistentry>
				<term><option>local_clientid</option> <replaceable>id</replaceable></term>
				<listitem>
					<para>Set the clientid to use on the local broker. If not
						defined, this defaults to
						<option>local.&lt;remote_clientid&gt;</option>. If you are
						bridging a broker to itself, it is important that
						local_clientid and remote_clientid do not match.</para>
				</listitem>
			</varlistentry>
			<varlistentry>
				<term><option>local_password</option> <replaceable>password</replaceable></term>
				<listitem>
					<para>Configure the password to be used when connecting
						this bridge to the local broker. This may be important
						when authentication and ACLs are being used.</para>
				</listitem>
			</varlistentry>
			<varlistentry>
				<term><option>local_username</option> <replaceable>username</replaceable></term>
				<listitem>
					<para>Configure the username to be used when connecting
						this bridge to the local broker. This may be important
						when authentication and ACLs are being used.</para>
				</listitem>
			</varlistentry>
			<varlistentry>
				<term><option>notifications</option> [ true | false ]</term>
				<listitem>
					<para>If set to <replaceable>true</replaceable>, publish
						notification messages to the local and remote brokers
						giving information about the state of the bridge
						connection. Retained messages are published to the
						topic $SYS/broker/connection/&lt;remote_clientid&gt;/state
						unless otherwise set with
						<option>notification_topic</option>s.  If the message
						is 1 then the connection is active, or 0 if the
						connection has failed. Defaults to
						<replaceable>true</replaceable>.</para>
					<para>This uses the Last Will and Testament (LWT) feature.</para>
				</listitem>
			</varlistentry>
			 <varlistentry>
				<term><option>notifications_local_only</option> [ true | false ]</term>
				<listitem>
					<para>If set to <replaceable>true</replaceable>, only publish
						notification messages to the local broker giving
						information about the state of the bridge connection.
						Defaults to <replaceable>false</replaceable>.</para>
				</listitem>
			</varlistentry>
			<varlistentry>
				<term><option>notification_topic</option> <replaceable>topic</replaceable></term>
				<listitem>
					<para>Choose the topic on which notifications will be
						published for this bridge. If not set the messages will
						be sent on the topic
						$SYS/broker/connection/&lt;remote_clientid&gt;/state.</para>
				</listitem>
			</varlistentry>
			<varlistentry>
				<term><option>remote_clientid</option> <replaceable>id</replaceable></term>
				<listitem>
					<para>Set the client id for this bridge connection. If not
						defined, this defaults to 'name.hostname', where name
						is the connection name and hostname is the hostname of
						this computer.</para>
					<para>This replaces the old "clientid" option to avoid
						confusion with local/remote sides of the bridge.
						"clientid" remains valid for the time being.</para>
				</listitem>
			</varlistentry>
			<varlistentry>
				<term><option>remote_password</option> <replaceable>value</replaceable></term>
				<listitem>
					<para>Configure a password for the bridge. This is used for
						authentication purposes when connecting to a broker
						that supports MQTT v3.1 and up and requires a username
						and/or password to connect. This option is only valid
						if a remote_username is also supplied.</para>
					<para>This replaces the old "password" option to avoid
						confusion with local/remote sides of the bridge.
						"password" remains valid for the time being.</para>
				</listitem>
			</varlistentry>
			<varlistentry>
				<term><option>remote_username</option> <replaceable>name</replaceable></term>
				<listitem>
					<para>Configure a username for the bridge. This is used for
						authentication purposes when connecting to a broker
						that supports MQTT v3.1 and up and requires a username
						and/or password to connect. See also the
						<option>remote_password</option> option.</para>
					<para>This replaces the old "username" option to avoid
						confusion with local/remote sides of the bridge.
						"username" remains valid for the time being.</para>
				</listitem>
			</varlistentry>
			<varlistentry>
				<term><option>restart_timeout</option> <replaceable>base cap</replaceable></term>
				<term><option>restart_timeout</option> <replaceable>constant</replaceable></term>
				<listitem>
					<para>Set the amount of time a bridge using the automatic
						start type will wait until attempting to reconnect.</para>
					<para>This option can be configured to use a constant delay
						time in seconds, or to use a backoff mechanism based on
						"Decorrelated Jitter", which adds a degree of
						randomness to when the restart occurs, starting at the
						base and increasing up to the cap. Set a constant
						timeout of 20 seconds:</para>
						<programlisting language="config">
restart_timeout 20</programlisting>
					<para>Set backoff with a base (start value) of 10 seconds and a cap (upper
						limit) of 60 seconds:</para>
						<programlisting language="config">
restart_timeout 10 30</programlisting>
					<para>Defaults to jitter with a base of 5 seconds and cap
						of 30 seconds.</para>
				</listitem>
			</varlistentry>
			<varlistentry>
				<term><option>round_robin</option> [ true | false ]</term>
				<listitem>
					<para>If the bridge has more than one address given in the
						address/addresses configuration, the round_robin option
						defines the behaviour of the bridge on a failure of the
						bridge connection. If round_robin is
						<replaceable>false</replaceable>, the default value,
						then the first address is treated as the main bridge
						connection. If the connection fails, the other
						secondary addresses will be attempted in turn. Whilst
						connected to a secondary bridge, the bridge will
						periodically attempt to reconnect to the main bridge
						until successful.</para>
					<para>If round_robin is <replaceable>true</replaceable>,
						then all addresses are treated as equals. If a
						connection fails, the next address will be tried and if
						successful will remain connected until it fails.</para>
				</listitem>
			</varlistentry>
			<varlistentry>
				<term><option>start_type</option> [ automatic | lazy | once ]</term>
				<listitem>
					<para>Set the start type of the bridge. This controls how
						the bridge starts and can be one of three types:
						<replaceable>automatic</replaceable>, <replaceable>lazy
						</replaceable>and <replaceable>once</replaceable>. Note
						that RSMB provides a fourth start type "manual" which
						isn't currently supported by mosquitto.</para>

					<para><replaceable>automatic</replaceable> is the default
						start type and means that the bridge connection will be
						started automatically when the broker starts and also
						restarted after a short delay (30 seconds) if the
						connection fails.</para>

					<para>Bridges using the <replaceable>lazy</replaceable>
						start type will be started automatically when the
						number of queued messages exceeds the number set with
						the <option>threshold</option> option. It will be
						stopped automatically after the time set by the
						<option>idle_timeout</option> parameter. Use this start
						type if you wish the connection to only be active when
						it is needed.</para>

					<para>A bridge using the <replaceable>once</replaceable>
						start type will be started automatically when the
						broker starts but will not be restarted if the
						connection fails.</para>
				</listitem>
			</varlistentry>
			<varlistentry>
				<term><option>threshold</option> <replaceable>count</replaceable></term>
				<listitem>
					<para>Set the number of messages that need to be queued for
						a bridge with lazy start type to be restarted.
						Defaults to 10 messages.</para>
				</listitem>
			</varlistentry>
			<varlistentry>
				<term><option>topic</option> <replaceable>pattern</replaceable> [[[ out | in | both ] qos-level] local-prefix remote-prefix]</term>
				<listitem>
					<para>Define a topic pattern to be shared between the two
						brokers. Any topics matching the pattern (which may
						include wildcards) are shared. The second parameter
						defines the direction that the messages will be shared
						in, so it is possible to import messages from a remote
						broker using <replaceable>in</replaceable>, export
						messages to a remote broker using
						<replaceable>out</replaceable> or share messages in
						both directions. If this parameter is not defined, the
						default of <replaceable>out</replaceable> is used. The
						QoS level defines the publish/subscribe QoS level used
						for this topic and defaults to 0.</para>
					<para>The <replaceable>local-prefix</replaceable> and
						<replaceable>remote-prefix</replaceable> options allow
						topics to be remapped when publishing to and receiving
						from remote brokers. This allows a topic tree from the
						local broker to be inserted into the topic tree of the
						remote broker at an appropriate place.</para>
					<para>For incoming topics, the bridge will prepend the
						pattern with the remote prefix and subscribe to the
						resulting topic on the remote broker. When a matching
						incoming message is received, the remote prefix will be
						removed from the topic and then the local prefix
						added.</para>
					<para>For outgoing topics, the bridge will prepend the
						pattern with the local prefix and subscribe to the
						resulting topic on the local broker. When an outgoing
						message is processed, the local prefix will be removed
						from the topic then the remote prefix added.</para>
					<para>When using topic mapping, an empty prefix can be
						defined using the place marker
						<replaceable>""</replaceable>. Using the empty marker
						for the topic itself is also valid. The table below
						defines what combination of empty or value is
						valid. The <option>Full Local Topic</option> and
						<option>Full Remote Topic</option> show the resulting
						topics that would be used on the local and remote ends
						of the bridge. For example, for the first table row if
						you publish to <option>L/topic</option> on the local
						broker, then the remote broker will receive a message
						on the topic <option>R/topic</option>.</para>

					<informaltable>
						<tgroup cols="6">
							<thead>
								<row>
									<entry><emphasis>Pattern</emphasis></entry>
									<entry><emphasis>Local Prefix</emphasis></entry>
									<entry><emphasis>Remote Prefix</emphasis></entry>
									<entry><emphasis>Validity</emphasis></entry>
									<entry><emphasis>Full Local Topic</emphasis></entry>
									<entry><emphasis>Full Remote Topic</emphasis></entry>
							</row>
							</thead>
							<tbody>
								<row><entry>pattern</entry><entry>L/</entry><entry>R/</entry><entry>valid</entry><entry>L/pattern</entry><entry>R/pattern</entry></row>
								<row><entry>pattern</entry><entry>L/</entry><entry>""</entry><entry>valid</entry><entry>L/pattern</entry><entry>pattern</entry></row>
								<row><entry>pattern</entry><entry>""</entry><entry>R/</entry><entry>valid</entry><entry>pattern</entry><entry>R/pattern</entry></row>
								<row><entry>pattern</entry><entry>""</entry><entry>""</entry><entry>valid (no remapping)</entry><entry>pattern</entry><entry>pattern</entry></row>
								<row><entry>""</entry><entry>local</entry><entry>remote</entry><entry>valid (remap single local topic to remote)</entry><entry>local</entry><entry>remote</entry></row>
								<row><entry>""</entry><entry>local</entry><entry>""</entry><entry>invalid</entry><entry></entry><entry></entry></row>
								<row><entry>""</entry><entry>""</entry><entry>remote</entry><entry>invalid</entry><entry></entry><entry></entry></row>
								<row><entry>""</entry><entry>""</entry><entry>""</entry><entry>invalid</entry><entry></entry><entry></entry></row>
							</tbody>
						</tgroup>
					</informaltable>
					<para>To remap an entire topic tree, use e.g.:</para>
					<programlisting language="config">
topic # both 2 local/topic/ remote/topic/</programlisting>

					<para>This option can be specified multiple times per
						bridge.</para>
					<para>Care must be taken to ensure that loops are not
						created with this option. If you are experiencing high
						CPU load from a broker, it is possible that you have a
						loop where each broker is forever forwarding each other
						the same messages.</para>
					<para>See also the <option>cleansession</option> option if
						you have messages arriving on unexpected topics when
						using incoming topics.</para>

					<example title="Bridge Topic Remapping" label="Bridge Topic Remapping">
						<para>The configuration below connects a bridge to the
							broker at <option>test.mosquitto.org</option>. It
							subscribes to the remote topic
							<option>$SYS/broker/clients/total</option> and
							republishes the messages received to the local topic
							<option>test/mosquitto/org/clients/total</option></para>
						<programlisting language="config">
connection test-mosquitto-org
address test.mosquitto.org
cleansession true
topic clients/total in 0 test/mosquitto/org/ $SYS/broker/
</programlisting></example>

				</listitem>
			</varlistentry>
			<varlistentry>
				<term><option>try_private</option> [ true | false ]</term>
				<listitem>
					<para>If try_private is set to
						<replaceable>true</replaceable>, the bridge will
						attempt to indicate to the remote broker that it is a
						bridge not an ordinary client. If successful, this
						means that loop detection will be more effective and
						that retained messages will be propagated correctly.
						Not all brokers support this feature so it may be
						necessary to set <option>try_private</option> to
						<replaceable>false</replaceable> if your bridge does
						not connect properly.</para>
					<para>Defaults to <replaceable>true</replaceable>.</para>
				</listitem>
			</varlistentry>
		</variablelist>
		<refsect2>
			<title>SSL/TLS Support</title>
			<para>The following options are available for all bridges to
				configure SSL/TLS support.</para>
			<variablelist>
				<varlistentry>
					<term><option>bridge_alpn</option> <replaceable>alpn</replaceable></term>
					<listitem>
						<para>Configure the application layer protocol negotiation
							option for the TLS session.  Useful for brokers that support
							both websockets and MQTT on the same port.</para>
					</listitem>
				</varlistentry>
				<varlistentry>
					<term><option>bridge_cafile</option> <replaceable>file path</replaceable></term>
					<listitem>
						<para>One of <option>bridge_cafile</option> or
							<option>bridge_capath</option> must be provided to
							allow SSL/TLS support.</para>
						<para>bridge_cafile is used to define the path to a file
							containing the PEM encoded CA certificates that
							have signed the certificate for the remote broker.
						</para>
					</listitem>
				</varlistentry>
				<varlistentry>
					<term><option>bridge_capath</option> <replaceable>file path</replaceable></term>
					<listitem>
						<para>One of <option>bridge_capath</option> or
							<option>bridge_cafile</option> must be provided to
							allow SSL/TLS support.</para>
						<para>bridge_capath is used to define the path to a
							directory containing the PEM encoded CA
							certificates that have signed the certificate for
							the remote broker. For bridge_capath to work
							correctly, the certificate files must have ".crt"
							as the file ending and you must run "openssl rehash
							&lt;path to bridge_capath&gt;" each time you
							add/remove a certificate.</para>
					</listitem>
				</varlistentry>
				<varlistentry>
					<term><option>bridge_certfile</option> <replaceable>file path</replaceable></term>
					<listitem>
						<para>Path to the PEM encoded client certificate for
							this bridge, if required by the remote
							broker.</para>
					</listitem>
				</varlistentry>
				<varlistentry>
					<term><option>bridge_identity</option> <replaceable>identity</replaceable></term>
					<listitem>
						<para>Pre-shared-key encryption provides an alternative
							to certificate based encryption. A bridge can be
							configured to use PSK with the
							<option>bridge_identity</option> and
							<option>bridge_psk</option> options.  This is the
							client identity used with PSK encryption. Only one
							of certificate and PSK based encryption can be used
							on one bridge at once.</para>
					</listitem>
				</varlistentry>
				<varlistentry>
					<term><option>bridge_insecure</option> [ true | false ]</term>
					<listitem>
						<para>When using certificate based TLS, the bridge will
							attempt to verify the hostname provided in the
							remote certificate matches the host/address being
							connected to. This may cause problems in testing
							scenarios, so <option>bridge_insecure</option> may
							be set to <replaceable>true</replaceable> to
							disable the hostname verification.</para>
						<para>Setting this option to
							<replaceable>true</replaceable> means that a
							malicious third party could potentially impersonate
							your server, so it should always be set to
							<replaceable>false</replaceable> in production
							environments.</para>
					</listitem>
				</varlistentry>
				<varlistentry>
					<term><option>bridge_keyfile</option> <replaceable>file path</replaceable></term>
					<listitem>
						<para>Path to the PEM encoded private key for this
							bridge, if required by the remote broker.</para>
					</listitem>
				</varlistentry>
				<varlistentry>
					<term><option>bridge_psk</option> <replaceable>key</replaceable></term>
					<listitem>
						<para>Pre-shared-key encryption provides an alternative
							to certificate based encryption. A bridge can be
							configured to use PSK with the
							<option>bridge_identity</option> and
							<option>bridge_psk</option> options.  This is the
							pre-shared-key in hexadecimal format with no "0x".
							Only one of certificate and PSK based encryption
							can be used on one bridge at once.</para>
					</listitem>
				</varlistentry>
				<varlistentry>
					<term><option>bridge_require_ocsp</option> [ true | false ]</term>
					<listitem>
						<para>When set to true, the bridge requires OCSP on the TLS
							connection it opens as client.</para>
					</listitem>
				</varlistentry>
				<varlistentry>
					<term><option>bridge_tls_version</option> <replaceable>version</replaceable></term>
					<listitem>
						<para>Configure the version of the TLS protocol to be
							used for this bridge. Possible values are
							<replaceable>tlsv1.3</replaceable>,
							<replaceable>tlsv1.2</replaceable> and
							<replaceable>tlsv1.1</replaceable>. Defaults to
							<replaceable>tlsv1.2</replaceable>. The remote
							broker must support the same version of TLS for the
							connection to succeed.</para>
					</listitem>
				</varlistentry>
			</variablelist>
		</refsect2>
	</refsect1>

	<refsect1>
		<title>Files</title>
		<para>mosquitto.conf</para>
	</refsect1>

	<refsect1>
		<title>Bugs</title>
		<para><command>mosquitto</command> bug information can be found at
			<ulink url="https://github.com/eclipse/mosquitto/issues"/></para>
	</refsect1>

	<refsect1>
		<title>See Also</title>
		<simplelist type="inline">
			<member>
				<citerefentry>
					<refentrytitle><link xlink:href="mosquitto-8.html">mosquitto</link></refentrytitle>
					<manvolnum>8</manvolnum>
				</citerefentry>
			</member>
			<member>
				<citerefentry>
					<refentrytitle><link xlink:href="mosquitto_passwd-1.html">mosquitto_passwd</link></refentrytitle>
					<manvolnum>1</manvolnum>
				</citerefentry>
			</member>
			<member>
				<citerefentry>
					<refentrytitle><link xlink:href="mosquitto-tls-7.html">mosquitto-tls</link></refentrytitle>
					<manvolnum>7</manvolnum>
				</citerefentry>
			</member>
			<member>
				<citerefentry>
					<refentrytitle><link xlink:href="mqtt-7.html">mqtt</link></refentrytitle>
					<manvolnum>7</manvolnum>
				</citerefentry>
			</member>
			<member>
				<citerefentry>
					<refentrytitle><link xlink:href="http://linux.die.net/man/5/limits.conf">limits.conf</link></refentrytitle>
					<manvolnum>5</manvolnum>
				</citerefentry>
			</member>
		</simplelist>
	</refsect1>

	<refsect1>
		<title>Author</title>
		<para>Roger Light <email>roger@atchoo.org</email></para>
	</refsect1>
</refentry>