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(3) 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);

SEE ALSO

       modbus_new_tcp(3) modbus_tcp_accept(3) modbus_tcp_pi_listen(3)

AUTHORS

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

libmodbus v3.1.6                                   12/09/2019                               MODBUS_TCP_LISTEN(3)