SYNOPSIS

modbus_t *modbus_new_tcp_pi(const char *node, const char *service);

DESCRIPTION

The modbus_new_tcp_pi() function shall allocate and initialize a modbus_t structure to communicate with a Modbus TCP IPv4 or Ipv6 server.

The node argument specifies the host name or IP address of the host to connect to, eg. 192.168.0.5 , ::1 or server.com.

The service argument is the service name/port number to connect to. To use the default Modbus port use the string "502". On many Unix systems, 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_pi() 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.

EXAMPLE

modbus_t *ctx;
ctx = modbus_new_tcp_pi("::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;
}

AUTHORS

The libmodbus documentation was written by Stéphane Raimbault <m[blue][email protected]m[][1]>

NOTES

1.

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