Silverlight Interaction with php in VB.NET

Introduction

Silverlight run on client side (Win/Mac/MoonLight)
Just copy and paste on LAMP server.
Communication use HTTP protocol.

Interface view

General description

?php if (isset($_POST["user"]))
{
list($usec, $sec) = explode(" ", microtime());
$ts = $sec.substr($usec,2,4);
// On crée le fichier message dans le dossier msg
    $fichier = fopen('msg/'.$ts, 'w+');
fwrite($fichier, stripslashes($_POST['data']));
fclose($fichier);
echo "0";
$dossier = opendir('msg');
while ($fichier = readdir($dossier))
{
if (!preg_match("#^[.]{1,2}[a-z0-9 -.]*#i",$fichier))
{
// On en profite pour purger les msg plus vieux que 15 secondes
 if ($fichier < ($ts - 150000))
{
unlink('msg/'.$fichier);
}
}
}
closedir($dossier);
}
?>  read_msg.php 

<?php
session_start();
// ouvrir le dosssier msg
$dossier = opendir('msg');
while ($fichier = readdir($dossier))
{
if (!preg_match("#^[.]{1,2}[a-z0-9 -.]*#i",$fichier))     
{ 
$files_array[] = $fichier;       
}
}
closedir($dossier);
sort($files_array);
foreach ($files_array as $key => $val)
{
if ($_SESSION['last_msg_ts'] < $val)
{
// Lit le message non lu
        readfile('msg/'.$val,'r');
// Indique le dernier message lu
        $_SESSION['last_msg_ts'] = $val;
exit;        
} 
}
?>

Post Message with WebClient

Private Sub SendMsg(ByVal Data As String)

ReadMsgTmr.Stop()

Try
Dim Client As New WebClient()
Client.Headers("Content-Type") = "application/x-www-form-urlencoded"
AddHandler Client.UploadStringCompleted, AddressOf SendMsgCompleted
Client.UploadStringAsync(New Uri(String.Format("{0}/write_msg.php", BASEPATH)), "Post",
"user=" & UsrTbx.Text & "&data=" & Data)

Catch ex As Exception

End Try

End Sub

Private Sub SendMsgCompleted(ByVal sender As Object, _
ByVal e As UploadStringCompletedEventArgs)