MODBUS_NEW_TCP

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 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.

RETURN VALUE

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.

ERRORS

EINVAL

An invalid IP address was given.

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_new_rtu(3) modbus_free(3)

AUTHORS

The libmodbus documentation was written by Stéphane Raimbault <stephane.raimbault@gmail.com [1] >

NOTES

mailto:stephane DOT raimbault AT gmail DOT com