PHP: Example Using Sockets to Connect to an Internet Server

When you need to talk to an Internet service such as http, ftp, SOAP, and so on, you will need to directly access this service via TCP or UDP sockets. This is a raw connection to another server, and you must know the details of the protocol you will be dealing with to properly send commands and receive data from them.

PHP provides a number of ways to talk with Internet servers, including a fsockopen() function and an entire BSD sockets extension that can be used. However, as of PHP 5, the streams extension has been greatly enhanced and is the preferred way to talk with Internet servers because it is highly configurable and powerful.

The following code is a small application that uses stream_socket_client() to connect to the free Internet Time Service provided by NIST. The time service works as follows: A TCP connection is made to port 13 on one of the NIST servers. When a connection is successfully created, the server immediately sends the response back with the current time.

<?php
if (!($tp = stream_socket_client('tcp://time.nist.gov:13', $err, $str))) {
    exit("ERROR: Failed to connect - {$err} - {$str}\n");

    exit("ERROR: Failed to connect - {$err_num} - {$err_string}\n");
}

fgets($tp);

echo trim(fgets($tp));

fclose($tp);
?>

To find out more information about the stream functions, see http://php.net/stream.

Hope it helps.