VB .net : How can a Server handle multiple clients simultaneosly at an instance

I am facing a problem in VB .net Client/Server application where I am successfully able to talk between them using TCPListener and TCPClient class usage. However, when I try to connect another Client to the same server on the same welcome port, it errors out throwing an exception or behaves very unexpectedly.

• Isn't it true that the Server conn开发者_运维问答ection is on a WELCOME PORT for all the clients, and that each client connected gets a new port to carry on its communication with the server AUTOMATICALLY (according to the Tomcat webserver working)?
• OR, is the above statement untrue and that the APP program handle the connections manually?

Pls clarify with an example in VB .net, if possible?

The answer to your question is 'Yes it is true'. I do not have VB.NET code ready but you can have a look at C# code here C# sockets handling multiple clients.

Okay.. pasting my server code here for your comments... Pls pardon my ignorance in coding and teach me if I were wrong. Thanks.

The Client is more obvious... so dint paste it here.

Server:

Public Class ServerSide2

...other stuff...

Public Class Packet

    Public packetType As String = "Data"
    Public packetOwnerIPAddress As String
    Public packetOwnerPort As String
    Public content As String

    Public Sub New(ByVal type As String, ByVal ip As String, ByVal port As String, ByVal data As String)

        packetType = type
        packetOwnerIPAddress = ip
        packetOwnerPort = port
        content = data

    End Sub
End Class

Public Class Worker

    Dim myLogger As Logger

    Dim name As String

    Dim ipClientAddress As IPAddress    'Client's IP address
    Dim ipClientPort As Integer = 22222 'Client listening on this port

    Dim tcpServer As TcpListener
    Dim tcpClient As TcpClient
    Dim networkStream As NetworkStream

    Dim readSize As Integer = 100

    Public Sub New(ByRef logger As Logger, ByVal id As String)

        myLogger = logger
        name = id

        myLogger.Trace("A new Worker object has been created for client: {0}", ipClientAddress)

    End Sub

    'Listener code
    Public Sub runClientHandler(ByVal ar As IAsyncResult)
        'code to listen to independent client
        Dim clientdata As String
        Dim numBytesRead As Integer = 0

        Thread.CurrentThread.Priority = ThreadPriority.Highest

        ' Get the listener that handles the client request.
        Dim listener As TcpListener = CType(ar.AsyncState, TcpListener)

        ' End the operation and display the received data on
        ' the console.
        tcpClient = listener.EndAcceptTcpClient(ar)

        ' Process the connection here. (Add the client to a
        ' server table, read data, etc.)
        myLogger.Info("Client connected completed")

        ' Signal the calling thread to continue.
        tcpClientConnected.Set()

        networkStream = tcpClient.GetStream()

        Dim ipEndPoint As IPEndPoint = tcpClient.Client.RemoteEndPoint
        ipClientAddress = ipEndPoint.Address

        myLogger.Info("A new Worker thread has been started.")

        While Not stopping

            myLogger.Trace("Start looping.")

            Dim bytes(readSize) As Byte

            numBytesRead = networkStream.Read(bytes, 0, bytes.Length)
            clientdata = Encoding.ASCII.GetString(bytes, 0, numBytesRead)

            'check for validity of the data
            If numBytesRead = 0 Then
                'connection lost
                myLogger.Trace("No data read.")
                Exit While
            End If

            If clientdata.Contains("SampleTest : {") Then

                'Message box the client data
                MsgBox("Test data from Client = " + clientdata)

                myLogger.Trace("Test data from Client = " + clientdata)

            ElseIf clientdata.Contains("Recieve Port : ") Then

                'Heed to Client's request on the port number server should reply
                Dim dest(5) As Char
                Dim destString As String = ""

                clientdata.CopyTo(15, dest, 0, clientdata.Length - 15)

                ipClientPort = CInt(CStr(dest))

                myLogger.Trace("Client Waiting on Port# : " + CStr(dest) + "for sorted packets.")

                'MsgBox("Client Waiting on Port# : " + CStr(dest))
            ElseIf clientdata.Contains("Packet Size : ") Then

                Dim dest(5) As Char
                Dim destString As String = ""
                clientdata.CopyTo(14, dest, 0, clientdata.Length - 14)

                readSize = CInt(CStr(dest))

                myLogger.Trace("Client's communicated Packet Size : " + CStr(dest))

            Else

                myLogger.Info("Begin to queue Data Packets.")

                While True

                    myLogger.Info("Data Packet.")

                    SyncLock Stats.locker

                        myLogger.Info("Got the lock.")

                        Stats.queueLength = Stats.requestQueue.Count

                        If Stats.queueLength < Stats.MAX_QUEUE_LENGTH Then
                            'Queue has some space to fit more packets

                            myLogger.Info("Queue has some space for this packet.")

                            Stats.packetNum = Stats.packetNum + 1
                            Dim newPacket As Packet = New Packet("Data", ipClientAddress.ToString, ipClientPort, clientdata)

                            Stats.requestQueue.Enqueue(newPacket)

                            Stats.sumQueueLength = Stats.sumQueueLength + Stats.requestQueue.Count
                            Stats.meanQueueLength = Stats.sumQueueLength / Stats.packetNum

                            myLogger.Info("Stats :: Packet #: {0}, QueueLength: {1}, MeanQueueLength: {2}.", Stats.packetNum, Stats.requestQueue.Count, Stats.meanQueueLength)
                        Else
                            'Queue is FULL, Ignore the packet
                            Stats.numDropPackets = Stats.numDropPackets + 1
                            myLogger.Info("Stats :: Dropped Packets: {0}.", Stats.numDropPackets)
                        End If

                    End SyncLock

                    numBytesRead = networkStream.Read(bytes, 0, bytes.Length)
                    clientdata = Encoding.ASCII.GetString(bytes, 0, numBytesRead)

                    'check for validity of the data
                    If numBytesRead = 0 Then
                        'connection lost
                        myLogger.Trace("No data read.")
                        Exit Sub
                    End If

                End While

            End If

        End While

        myLogger.Trace("End looping.")

    End Sub

End Class

Sub ListeningThread()
    Dim count As Integer = 0

    tcpServer = New TcpListener(ipAddress, iPort)
    tcpServer.Start()

    Try
        While Not stopping And count < Stats.MAX_CLIENTS

            count = count + 1
            Dim workerName = "worker:" + CStr(count)
            Dim worker As Worker = New Worker(logger, workerName)

            logger.Info("Waiting for a client to connect")
            DoBeginAcceptTcpClient(worker, tcpServer)

            logger.Info("Connected to {0}.", workerName)

            'Add the client to the hashTable
            'ADITYA later clients.Add(workerName, client)

            If SortAndSendThrd Is Nothing Then
                'Start a new thread
                SortAndSendThrd = New Thread(SortAndSendThrdStart)
                SortAndSendThrd.Priority = ThreadPriority.Highest
            End If

            If Not SortAndSendThrd.IsAlive Then
                SortAndSendThrd.Start()
                logger.Debug("Started off a Sort thread")
            End If

            'Dim i As Integer = 0
            'Dim objValue As Object

            'For Each objKey In clients.Keys
            '    objValue = clients.Item(objKey)
            '    'MsgBox("[" & objKey.ToString & ", " & objValue.ToString & "]")
            'Next objKey

        End While
    Catch ex As IOException
        ToolStripStatusLabel1.Text = "ERROR : SocketException: {0}" + ex.Message
        'MsgBox(ex.Message + ":::2")
    Catch ex As SocketException
        ToolStripStatusLabel1.Text = "ERROR : SocketException: {0}" + ex.Message
        'MsgBox(ex.Message + ":::1")
    End Try

    'tcpServer.Stop()
    'client.Close()

    logger.Debug("The Server's listening handler has come to an end.")

End Sub
End Class

When I try to connect a second client to this, the server drops the connection 1 and behaves unpredictably.