Before I show you how to expand the sample TCP server developed in the first tutorial, first allow me list the full source code that creates it, including the procedural script, the "createSocketServer()" function that I defined before, and finally the "SocketServer" class. Here are the corresponding signatures for each case:

/*
//**************************************************************
// procedural script for building a TCP server
//**************************************************************
*/
// define  TCP port & local host
$port=1234;
$host='127.0.0.1';
set_time_limit(0);
// create low level socket
if(!$socket=socket_create(AF_INET,SOCK_STREAM,0)){
    trigger_error('Error creating new socket',E_USER_ERROR);
}          
// tie up socket to TCP port
if(!socket_bind($socket,$host,$port)){
    trigger_error('Error binding socket to TCP port',E_USER_ERROR);
}
// begin listening connections
if(!socket_listen($socket)){
    trigger_error('Error listening socket
connections',E_USER_ERROR);
}
// create communication socket
if(!$comSocket=socket_accept($socket)){
    trigger_error('Error creating communication
socket',E_USER_ERROR);
}
// read socket input
$socketInput=socket_read($comSocket,1024);
// convert to uppercase socket input
$socketOutput=strtoupper(trim($socketInput))."n";
// write data back to socket server
if(!socket_write($comSocket,$socketOutput,strlen($socketOutput)))
{
    trigger_error('Error writing socket output',E_USER_ERROR);
}
// close sockets
socket_close($comSocket);
socket_close($socket);

*/
//**************************************************************
// user-defined function for building a TCP server
//**************************************************************
/*
function createSocketServer($host='127.0.0.1',$port=1234){
    if(!preg_match("/^d{1,3}.d{1,3}.d{1,3}.d{1,3}
$/",$host)){
        trigger_error('Invalid IP address format.',E_USER_ERROR);
    }
    if(!is_int($port)||$port<1||$port>65535){
        trigger_error('Invalid TCP port number.',E_USER_ERROR);
    }
    set_time_limit(0);
    // create low level socket
    if(!$socket=socket_create(AF_INET,SOCK_STREAM,0)){
        trigger_error('Error creating new socket.',E_USER_ERROR);
    }
    // bind socket to TCP port
    if(!socket_bind($socket,$host,$port)){
        trigger_error('Error binding socket to TCP
port.',E_USER_ERROR);
    }
    // begin listening connections
    if(!socket_listen($socket)){
         trigger_error('Error listening socket
connections.',E_USER_ERROR);
    }
    // create communication socket
    if(!$comSocket=socket_accept($socket)){
        trigger_error('Error creating communication
socket.',E_USER_ERROR);
    }
    // read socket input
    $socketInput=socket_read($comSocket,1024);
    // convert to uppercase socket input 
    $socketOutput=strtoupper(trim($socketInput))."n";
    // write data back to socket server
    if(!socket_write($comSocket,$socketOutput,strlen
($socketOutput))){
        trigger_error('Error writing socket
output',E_USER_ERROR);
    }
    // close sockets
    socket_close($comSocket);
    socket_close($socket);
}

*/
//**************************************************************
// PHP class for building a TCP server
//**************************************************************
*/
class SocketServer{
    var $host;
    var $port;
    function  SocketServer($host='127.0.0.1',$port=1234){
        if(!preg_match("/^d{1,3}.d{1,3}.d{1,3}.d{1,3}
$/",$host)){
            trigger_error('Invalid IP address
format.',E_USER_ERROR);
        }
        if(!is_int($port)||$port<1||$port>65535){
            trigger_error('Invalid TCP port
number.',E_USER_ERROR);
        }
        $this->host=$host;
        $this->port=$port;
        $this->connect();
    }
    function connect(){
        set_time_limit(0);
        // create low level socket
        if(!$socket=socket_create(AF_INET,SOCK_STREAM,0)){
            trigger_error('Error creating new
socket.',E_USER_ERROR);
        }
        // bind socket to TCP port
        if(!socket_bind($socket,$this->host,$this->port)){
            trigger_error('Error binding socket to TCP
port.',E_USER_ERROR);
        }
        // begin listening connections
        if(!socket_listen($socket)){
            trigger_error('Error listening socket
connections.',E_USER_ERROR);
        }
        // create communication socket
        if(!$comSocket=socket_accept($socket)){
            trigger_error('Error creating communication
socket.',E_USER_ERROR);
        }
        // read socket input
        $socketInput=socket_read($comSocket,1024);
        // convert to uppercase socket input 
        $socketOutput=strtoupper(trim($socketInput))."n";
        // write data back to socket server
        if(!socket_write($comSocket,$socketOutput,strlen
($socketOutput))){
            trigger_error('Error writing socket
output',E_USER_ERROR);
        }
        // close sockets
        socket_close($comSocket);
        socket_close($socket);
    }
}

Right, as you can see above, I listed all the source code corresponding to both procedural and object-oriented approaches, in order to create a sample TCP server. However, as you'll recall, all these examples demonstrate how to build a socket server that processes one request at a time; it is unable to handle multiple petitions.

Bearing in mind this limitation, in the next section I'll show you how to expand the pertinent TCP server in such a way that it will be able to process multiple client requests.

To learn how this will be done, please keep on reading.