Imports System
Imports System.Net
Imports System.Net.Sockets
Imports System.Text
Imports System.Web.UI.WebControls
Namespace MyApps

'Classe per la connessione via socket
  Public Class clSocket
    Private s As Socket

    Private Fdns As String
    Public ReadOnly Property dns() As String
      Get
        Return Fdns
      End Get
    End Property

    Private Fport As Integer
    Public ReadOnly Property port() As Integer
      Get
        Return Fport
      End Get
    End Property

    Private Fuser As String
    Public ReadOnly Property user() As String
      Get
        Return Fuser
      End Get
    End Property

    Private Fpassword As String
    Public ReadOnly Property password() As String
      Get
        Return Fpassword
      End Get
    End Property

    Public Sub clSocket()
    End Sub

    'Costruttore
    ' <param name="dns">Il server a cui collegarsi</param>
    ' <param name="port">La porta</param>
    ' <param name="user">Nome utente</param>
    ' <param name="password">Password</param>
    Public Sub clSocket(ByVal dns As String, ByVal port As Integer, ByVal user As String, ByVal password As String)
      Fdns = dns
      Fport = port
      Fuser = user
      Fpassword = password
      Connect()
    End Sub

    ' Crea la connessione al socket
    ' <returns>True se va a buon fine</returns>
    Public Function Connect() As Boolean
      s = Nothing
      Dim hostEndPoint As IPEndPoint
      Dim hostAddress As IPAddress = Nothing
      Dim hostInfo As IPHostEntry = System.Net.Dns.Resolve(Me.dns)
      Dim IPaddresses() As IPAddress = hostInfo.AddressList
      hostAddress = IPaddresses(0)
      hostEndPoint = New IPEndPoint(hostAddress, Me.port)
      Try
        s = New Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp)
        s.Connect(hostEndPoint)
        Return s.Connected
      Catch err As Exception
        s.Shutdown(SocketShutdown.Both)
        s.Close()
      Throw err
      End Try
    End Function

    ' Esegue il login
    ' <returns>True se va a buon fine</returns>
    Public Function login() As Boolean
      SendCommand("USER " + Me.user)
      SendCommand("PASS " + Me.password)
      If (ReceiveCommand("login").IndexOf("200 login OK, proceed\r\n\0") > -1) Then
        clearBuffer()
        Return True
      Else
        Return False
      End If
    End Function

    ' Esegue la disconnessione
    Public Sub Disconnect()
      s.Shutdown(SocketShutdown.Both)
      s.Close()
      s = Nothing
    End Sub

    ' Invia un comando via socket
    ' <param name="command">Il nome del comando inviato</param>
    Public Sub SendCommand(ByVal command As String)
      Dim msg As Byte()
      msg = Encoding.ASCII.GetBytes(command + "\r\n")
      s.Send(msg, 0, msg.Length, SocketFlags.None)
    End Sub

    ' Legge la risposta (dopo l'invio di un comando
    ' <param name="sTerminate">Il carattere di fine che cia aspettiamo</param>
    ' <returns>La risposta</returns>
    Public Function ReceiveCommand(ByVal sTerminate As String) As String
      Dim str As String = ""
      Dim iRx As Integer = 0
      Dim buffer(1024) As Byte
      While (True)
        If (s.Available > 0) Then
          iRx = s.Receive(buffer)
          str += Encoding.ASCII.GetString(buffer)
          If str.IndexOf(sTerminate) > -1 Or str.IndexOf("512") > -1 Then
            Return str
          End If
        End If
      End While
    End Function

    ' Svuota il buffer di ricazione
    Public Sub clearBuffer()
      Dim iRx As Integer
      Dim buffer(1024) As Byte
      While (s.Poll(100000, SelectMode.SelectRead))
        iRx = s.Receive(buffer)
      End While
    End Sub
  End Class
End Namespace

'istanzio la classe
Dim cs As clSocket = New clSocket("web.myDomain.com", port, User, password)
Try
  'eseguo il login
  cs.login()
  'invio un comando
  cs.SendCommand("NOMECOMANDO")
  'leggo la risposta
  cs.ReceiveCommand("ENDCHAR")
Catch
  'gestione eccezioni
Finally
  cs.Disconnect()
End Try