libmodbus/docs/modbus_set_socket.md

modbus_set_socket

Name

modbus_set_socket - set socket of the context

Synopsis

int modbus_set_socket(modbus_t *ctx, int s);

Description

The modbus_set_socket() function shall set the socket or file descriptor in the libmodbus context. This function is useful for managing multiple client connections to the same server.

Return value

The function shall return 0 if successful. Otherwise it shall return -1 and set errno.

Example

ctx = modbus_new_tcp("127.0.0.1", 1502);
server_socket = modbus_tcp_listen(ctx, NB_CONNECTION);

FD_ZERO(&rdset);
FD_SET(server_socket, &rdset);

/* .... */

if (FD_ISSET(master_socket, &rdset)) {
    modbus_set_socket(ctx, master_socket);
    rc = modbus_receive(ctx, query);
    if (rc != -1) {
        modbus_reply(ctx, query, rc, mb_mapping);
    }
}

See also

• modbus_get_socket