Imports System.Net, Microsoft.Win32
Imports System.Management
Imports System.IO
Imports System.Security.Cryptography
Imports System.Text
Imports System.Threading
Public Class Form1

    Dim wc As New WebClient()

    Private Sub Form1_FormClosing(sender As Object, e As FormClosingEventArgs) Handles Me.FormClosing
        Remove()
    End Sub
    Private Sub Form_load(sender As Object, e As EventArgs) Handles MyBase.Load
        Dim Checker As New Thread(AddressOf Check)
        Checker.Start()
    End Sub

    Sub Add()
        Try
            Dim richiesta As HttpWebRequest = DirectCast(WebRequest.Create("http://localhost/test/utenti.txt"), HttpWebRequest)
            Dim risposta As HttpWebResponse = DirectCast(richiesta.GetResponse(), HttpWebResponse)
            Dim sr As New StreamReader(risposta.GetResponseStream())
            Dim usernow As String = sr.ReadToEnd
            wc.DownloadString("http://localhost/test/users.php?utenti=" & usernow + 1)
            Label1.Text = "Online users: " & usernow + 1
        Catch ex As Exception
            MessageBox.Show("Error: " & ex.Message, "Error", MessageBoxButtons.OK, _
                MessageBoxIcon.Error)
            Environment.Exit(0)
        End Try
    End Sub

    Sub Remove()
        Try
            Dim richiesta As HttpWebRequest = DirectCast(WebRequest.Create("http://localhost/test/utenti.txt"), HttpWebRequest)
            Dim risposta As HttpWebResponse = DirectCast(richiesta.GetResponse(), HttpWebResponse)
            Dim streamr As New StreamReader(risposta.GetResponseStream())
            Dim users As String = streamr.ReadToEnd
            wc.DownloadString("http://localhost/test/users.php?utenti=" & users - 1)
            Label1.Text = "Online users: " & users - 1
        Catch ex As Exception
            MessageBox.Show("Error: " & ex.Message, "Error", MessageBoxButtons.OK, _
    MessageBoxIcon.Error)
            Environment.Exit(0)
        End Try

    End Sub


    Delegate Sub _Check()
    Sub Check()
        If InvokeRequired Then
            Invoke(New _Check(AddressOf Check))
        Else
            Try
                Dim richiesta As HttpWebRequest = DirectCast(WebRequest.Create("http://localhost/test/utenti.txt"), HttpWebRequest)
                Dim risposta As HttpWebResponse = DirectCast(richiesta.GetResponse(), HttpWebResponse)
                Dim l As New StreamReader(risposta.GetResponseStream())
                Label1.Text = String.Format("Online user: {0}", l.ReadToEnd)
            Catch Ex As Exception 'Clauspla catch....
                MessageBox.Show("Error: " & Ex.Message, "Error", MessageBoxButtons.OK, _
                                MessageBoxIcon.Error)
                Environment.Exit(0)
            End Try
        End If
    End Sub
    Private Sub Form1_Load(sender As Object, e As System.EventArgs) Handles MyBase.Load
        Add()
    End Sub
End Class
_________________________________________________________________________________________________________________________________

.PHP


<?php
$utenti=$_GET['utenti'];
$file = "utenti.txt";
$open = fopen($file;
$write = fwrite ($open, $testo);
fclose($open);
?>