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 ⟨modbus_new_tcp.md⟩ 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 ⟨modbus_new_tcp.md⟩

    •   modbus_tcp_accept ⟨modbus_tcp_accept.md⟩

    •   modbus_tcp_pi_listen ⟨modbus_tcp_pi_listen.md⟩