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);
    }
}