modbus_tcp_listen(3) ==================== 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 linkmb: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 [source,c] ------------------- ... /* 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 -------- linkmb:modbus_new_tcp[3] linkmb:modbus_tcp_accept[3] linkmb:modbus_tcp_pi_listen[3] AUTHORS ------- The libmodbus documentation was written by Stéphane Raimbault