modbus_new_tcp(3) ================= NAME ---- modbus_new_tcp - create a libmodbus context for TCP/IPv4 SYNOPSIS -------- *modbus_t *modbus_new_tcp(const char *'ip', int 'port');* DESCRIPTION ----------- The *modbus_new_tcp()* function shall allocate and initialize a modbus_t structure to communicate with a Modbus TCP IPv4 server. The _ip_ argument specifies the IP address of the server to which the client wants to establish a connection. A NULL value can be used to listen any addresses in server mode. The _port_ argument is the TCP port to use. Set the port to `MODBUS_TCP_DEFAULT_PORT` to use the default one (502). It’s convenient to use a port number greater than or equal to 1024 because it’s not necessary to have administrator privileges. RETURN VALUE ------------ The function shall return a pointer to a *modbus_t* structure if successful. Otherwise it shall return NULL and set errno to one of the values defined below. ERRORS ------ *EINVAL*:: An invalid IP address was given. EXAMPLE ------- [source,c] ------------------- modbus_t *ctx; ctx = modbus_new_tcp("127.0.0.1", 1502); if (ctx == NULL) { fprintf(stderr, "Unable to allocate libmodbus context\n"); return -1; } if (modbus_connect(ctx) == -1) { fprintf(stderr, "Connection failed: %s\n", modbus_strerror(errno)); modbus_free(ctx); return -1; } ------------------- SEE ALSO -------- linkmb:modbus_tcp_listen[3] linkmb:modbus_free[3] AUTHORS ------- The libmodbus documentation was written by Stéphane Raimbault