// Set the ip and port we will listen on
$host = '127.0.0.1';
$port = 20000;

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);
}

# reuse socket tweak
  if (!socket_set_option($socket, SOL_SOCKET, SO_REUSEADDR, 1)) {
    echo socket_strerror(socket_last_error($socket));
    exit;
  }

// tie up socket to TCP port
if(!socket_bind($socket,$host,$port)){
    trigger_error('Error binding socket to TCP host:'.$host.', port:'.$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);

//write data to file
....

// close sockets
socket_close($comSocket);

socket_close($socket);

PHP Warning:  set_time_limit(): Cannot set time limit
PHP Warning:  socket_bind() unable to bind address [98]: Address already in use
Could not bind to address