modbus_new_tcp(3) Manual Page

modbus_t *modbus_new_tcp(const char *ip, int port);

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 etablish a connection.

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.

The modbus_new_tcp() 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.

modbus_new_rtu(3) modbus_free(3)

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