modbus_tcp_listen.md 1.4 KB
modbus_tcp_listen
Name
modbus_tcp_listen - create and listen a TCP Modbus socket (IPv4)
Synopsis
int modbus_tcp_listen(modbus_t *ctx, int nb_connection);
Description
The modbus_tcp_listen() function shall create a socket and listen to maximum
nb_connection incoming connections on the specified IP address. The context
ctx must be allocated and initialized with modbus_new_tcp before to
set the IP address to listen, if IP address is set to NULL or '0.0.0.0', any addresses will be
listen.
Return value
The function shall return a new socket if successful. Otherwise it shall return -1 and set errno.
Example
For detailed examples, see source files in tests directory:
- unit-test-server.c, simple but handle only one connection
bandwidth-server-many-up.c, handles several connections at once
... /* To listen any addresses on port 502 */ ctx = modbus_new_tcp(NULL, 502); /* Handle until 10 established connections */ server_socket = modbus_tcp_listen(ctx, 10); /* Clear the reference set of socket */ FD_ZERO(&refset); /* Add the server socket */ FD_SET(server_socket, &refset); if (select(server_socket + 1, &refset, NULL, NULL, NULL) == -1) { } ... close(server_socket); modbus_free(ctx);