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.

PHP: Communicating with an LDAP Server Example

LDAP(Lightweight Directory Access Protocol) is used to talk with directory services for retrieving and modifying data. It is not a relational database system. LDAP is simply a system that provides a hierarchical organization of data. LDAP's most common use currently is for corporate address and email books, allowing for all information about each employee to be stored and retrieved as needed.

PHP provides commands to communicate to an LDAP server that are easy to use. A typical set of commands would be to connect to the server, bind (authenticate), search for some data, and then handle the data. The only problem is that the structure of each LDAP server is completely different based on how the administrator set it up, just like every database system is different. Therefore, you must understand the structure of the tree hierarchy of that LDAP server to work with it.

In the following code, we connect to a fictional LDAP server that just has three levels of hierarchy with the top one being c = Country Code, then under that o = Organization, and then below that un = User Name. (Nominally, of course, there would be more information beneath that level; however, this is all we need for our example.)

<?php
if (!($lc = ldap_connect('ldap.example.com'))) {
    die("ERROR: Can't connect to the LDAP server\n");
}

//Anonymous bind (read only access)
ldap_bind($lc);

// Search for anyone in the IT department
// with a username starting with 'e'
$res = ldap_search($lc, 'o=Information Technology, c=US', 'un=e*');

// Now, let's read all results from our search:
$data = ldap_get_entries($lc, $res);

// Loop over them all, echoing the data out:
for ($i=0; $i < $data['count']; $i++) {
    echo "Full entry (distinguished name - dn): {$data[$i]['dn']}
\n";
    echo "Username: {$data[$i]['un'][0]}
\n";
}
?>

Like many other extensions of the language, LDAP support must be compiled into the server (or enabled on Windows) before you can use it. Also, we have only scratched the surface of what the full LDAP extension can do. To explore more, read the documentation at http://php.net/ldap.

Hope it helps.