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.

       ENOMEM
           Out of memory. Possibly, the application hits its memory limit and/or whole system is
           running out of memory.

EXAMPLE

           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

       modbus_tcp_listen(3) modbus_free(3)

AUTHORS

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