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