libmodbus/doc/modbus_set_error_recovery.txt

modbus_set_error_recovery(3)
============================


NAME
----
modbus_set_error_recovery - set the error recovery mode


SYNOPSIS
--------
*int modbus_set_error_recovery(modbus_t *'ctx', modbus_error_recovery_mode 'error_recovery');*


DESCRIPTION
-----------
The _modbus_set_error_recovery()_ function shall set the error recovery mode to
apply when the connection fails or the date received are not expected.

By default there is no error recovery ('MODBUS_ERROR_RECOVERY_NONE') so the
application is responsible for controlling the error values returned by
libmodbus functions and for handling them if necessary.

When 'MODBUS_ERROR_RECOVERY_LINK' is set, the library will attempt an immediate
reconnection (which may hang for several seconds if the network to the remote
target unit is down). This mode will try a infinite close/connect loop until
success on send call and will just try one time to retablish the connection on
select/read calls (if the connecton was down, the values to read are certainly
not available anymore after reconnection, except for slave/server). This mode
will also run flush requests after a delay based on the current response timeout
in some situations (eg. timeout of select call).

When 'MODBUS_ERROR_RECOVERY_PROTOCOL' is set, a sleep and flush sequence will be
used to cleanup the ongoing communication, this can occurs when the message
length is invalid, the TID is wrong or the received function code is not the
expected one.

The modes are mask values and so they are complementary.

It's not recommended to enable error recovery for slave/server.


RETURN VALUE
------------
The _modbus_set_error_recovery()_ function shall return 0 if
successful. Otherwise it shall return -1 and set errno to one of the values
defined below.


ERRORS
------
*EINVAL*::
The value of the argument 'error_recovery' is not positive.


EXAMPLE
-------
[source,c]
-------------------
modbus_set_error_recovery(ctx,
                          MODBUS_ERROR_RECOVERY_LINK |
                          MODBUS_ERROR_RECOVERY_PROTOCOL);
-------------------

AUTHORS
-------
The libmodbus documentation was written by Stéphane Raimbault
<stephane.raimbault@gmail.com>