tcp/ip - consecutive serialized objects not deserializing. help!

[stopworth]

Hi,

This is my first post on here--I've been teaching myself VB via forums like this and MSDN for about 2 years now.

I'm programming a computerized economics experiment, and I'm using a communications package that a guy I worked

with developed. He and I have been going back and forth trying to figure out what the heck is going on.

The upshot of the communications package is that there's a serializeable MQMessage class that we send back and forth, essentially just a package of an integer (Type), string (Text), and Object (Data). Most of the time, this goes according to plan.

The problem is this: If the client receives two or more messages back-to-back, the client stops raising the MessageArrived event. (and presumably, the same would hold true for the server--I should test this, but jeez-oh-man, I've been running test after test for the last week).

It's still connected, as on disconnect it throws the "Socket forcibly closed" exception. When it receives multiple messages sequentially, it's still receiving the data, it just never knows when the first message ends, and the buffer just keeps filling and filling. The problem seems to be that it can never successfully Deserialize the MQMessage object, and so it returns Nothing on the getCompletedMessage function and just keeps adding to the buffer (ABuffer.Length goes 1024, 2048, etc.). Any ideas on how to solve this would be GREATLY appreciated (I've been frustrated by this for a year or so, and have only recently taken upon myself to learn how the hell the TCP/IP part of this works to see if I can't find a solution.).

Code to follow.

--stopworth

[stopworth]

This is the server code:

Imports System
Imports System.Net
Imports System.Net.Sockets
Imports System.Text
Imports System.Threading

Public Class MQmonitor

'Delegates

    Public Delegate Sub MessageArrivedCallBack(ByVal Subject As Integer, ByVal message As MQMessage)
    Public Delegate Sub TextArrivedCallBack(ByVal Subject As Integer, ByVal text As String)
    Public Delegate Sub NewSubjectConnectedCallBack(ByVal Subject As Integer, ByVal UserName As String)
    Public Delegate Sub SubjectReconnectedCallBack(ByVal Subject As Integer, ByVal UserName As String)
    Public Delegate Sub SubjectDisconnectedCallBack(ByVal Subject As Integer, ByVal UserName As String)
    Public Delegate Sub Socket_ErrorCallBack(ByVal e As Exception)

'Events
    Public Event MessageArrived(ByVal Subject As Integer, ByVal message As MQMessage)
    Public Event TextArrived(ByVal Subject As Integer, ByVal text As String)
    Public Event NewSubjectConnected(ByVal Subject As Integer, ByVal UserName As String)
    Public Event SubjectReconnected(ByVal Subject As Integer, ByVal UserName As String)
    Public Event SubjectDisconnected(ByVal Subject As Integer, ByVal UserName As String)
    Public Event Socket_Error(ByVal e As Exception)

'Fields & Private Vars
    Private m_InitSubjectNumber As String = 101
    Private SubjectNameTable As New Hashtable
    Private StateTable As New Hashtable
    Private isExperimentStart As Boolean
    Dim m_ExpInstance As String
    Dim m_ExpName As String
    Dim m_port As Integer = "2955"
    Dim tcpListener As TcpListener
    Dim m_start As Boolean = False
    Dim allClients As ArrayList = New ArrayList()
    Dim currentID As Integer = 101
    Dim listener As Socket

'Properties
  -    Public Property ExpInstance() As String 
  -    Public Property ExpName() As String
  -    Public Property Port() As Integer
  -    Public Property InitialSubjectNumber() As Integer

'Public Functions
'SendMessage(m as MQMessage, x as Integer) As Exception : Send MQMessage object m to Client with SubjectID x
'BroadCastMessage(m as MQMessage) as Exception: Send MQMessage object m to all clients
'OpenServer() as Exception: Sets up SubjectIDs and opens a TCPListener on m_port() 


'Code

    Public Function SendMessage(ByVal msg As MQMessage, ByVal SubjectID As Integer) As Exception
        Try
            Dim state As ExpStateObject = StateTable.Item(SubjectID)
            Me.Send(state, msg)
        Catch ex As Exception
            Return ex
        End Try
        Return Nothing
    End Function
    
    Public Function BroadCastMessage(ByVal msg As MQMessage) As Exception
        Try
            Dim myEnumerator As IDictionaryEnumerator = StateTable.GetEnumerator()
            Dim state As ExpStateObject

            While myEnumerator.MoveNext()
                state = myEnumerator.Value
                Me.Send(state, msg)
            End While

        Catch ex As Exception
            Return ex
        End Try
        Return Nothing
    End Function

    Public Function OpenServer() As Exception

	'Initializes the SubjectNumber (unique ID) and TCPListener and starts the TCPListener.

        If (m_start) Then
            Return New Exception("Queue has already been started")
        End If

        currentID = m_InitSubjectNumber
        m_start = True
        Dim bytes() As Byte = New [Byte](1024) {}

        ' Establish the local endpoint for the socket.
        ' The DNS name of the computer
        ' running the listener is "host.contoso.com".


        ' Bind the socket to the local endpoint and listen for incoming 
        ' connections.
        Try
            Dim ipHostInfo As IPHostEntry = Dns.GetHostEntry(Dns.GetHostName)

            Dim ipAddress As IPAddress = ipHostInfo.AddressList(0)
            For Each ip As IPAddress In ipHostInfo.AddressList
                If (ip.AddressFamily = AddressFamily.InterNetwork) Then
                    ipAddress = ip
                    Exit For
                End If
            Next

            Dim localEndPoint As New IPEndPoint(ipAddress, m_port)

            ' Intializes a TCP/IP socket.
            Dim listener As New Socket(AddressFamily.InterNetwork, _
                SocketType.Stream, ProtocolType.Tcp)

            listener.Bind(localEndPoint)
            listener.Listen(10)

            ' Start an asynchronous socket to listen for connections.
            listener.BeginAccept(New AsyncCallback(AddressOf AcceptCallback), _
            listener)

        Catch e As Exception
            Return e
        End Try

        Return Nothing
    End Function

    Private Sub AcceptCallback(ByVal ar As IAsyncResult)

        ' Get the socket that handles the client request.
        Dim listener As Socket = CType(ar.AsyncState, Socket)
        Dim handler As Socket = listener.EndAccept(ar)
        handler.NoDelay = True

        ' Create the state object.
        Dim state As New ExpStateObject()
        state.workSocket = handler
        handler.BeginReceive(state.buffer, 0, ExpStateObject.BufferSize, 0, _
        New AsyncCallback(AddressOf ReceiveCallback), state)
        listener.BeginAccept(New AsyncCallback(AddressOf AcceptCallback), listener)

    End Sub 'AcceptCallback
    Private Sub ReceiveCallback(ByVal ar As IAsyncResult)
        Dim content As [String] = [String].Empty
        ' Retrieve the state object and the handler socket
        ' from the asynchronous state object.
        Dim state As ExpStateObject = CType(ar.AsyncState, ExpStateObject)
        Dim handler As Socket = state.workSocket

        ' Read data from client socket. 
        Try
            Dim bytesRead As Integer = handler.EndReceive(ar)

            If bytesRead > 0 Then

                Dim message As MQMessage = state.getCompletedMessage(bytesRead)
                
		If Not (message Is Nothing) Then
                    messageRecieved(state, message)
                End If
                handler.BeginReceive(state.buffer, 0, ExpStateObject.BufferSize, _
                        0, New AsyncCallback(AddressOf ReceiveCallback), state)

            End If
        Catch ex As Exception
            RaiseEvent Socket_Error(ex)
        End Try


    End Sub 'ReadCallback
    Private Sub messageRecieved(ByRef state As ExpStateObject, ByVal msg As MQMessage)
        If msg.Type = MQMessage.TYPE_SUBJECT_CONNECTION_MESSAGE Then
            connectionRequest(state, msg)
        ElseIf msg.Type = MQMessage.TYPE_PLAIN_TEXT_MESSAGE Then
            RaiseEvent TextArrived(state.SubjectID, msg.Text)
        Else
            RaiseEvent MessageArrived(state.SubjectID, msg)
        End If
    End Sub
    Private Function connectionRequest(ByRef state As ExpStateObject, ByVal msg As MQMessage) As Integer
        Dim userName As String = CType(msg.Data, MQMessage.SubjectConnectionMessage).UserName
        Dim ID As Integer

        If isExperimentStart Then
            If SubjectNameTable.ContainsKey(userName) Then
                ID = SubjectNameTable.Item(userName)
                state.SubjectID = ID
                updateStateTable(state, ID)
                ReSendMessage(ID)


            End If
        Else
            If SubjectNameTable.ContainsKey(userName) Then
                Send(state, New MQMessage(MQMessage.TYPE_DUPLICATE_USERNAME_MESSAGE))
            Else
                ID = currentID
                currentID += 1
                state.SubjectID = ID
                SubjectNameTable.Add(userName, ID)
                updateStateTable(state, ID)
                RaiseEvent NewSubjectConnected(ID, CType(msg.Data, MQMessage.SubjectConnectionMessage).UserName)


                Dim message As New MQMessage(MQMessage.TYPE_LOGIN_CONFIRMED_MESSAGE)
                message.Data = ID
                Send(state, message)

            End If
        End If

    End Function 'connectionRequest

    Private Sub updateStateTable(ByVal state As ExpStateObject, ByVal subjectID As Integer)
        If StateTable.ContainsKey(subjectID) Then
            Dim oldState As ExpStateObject = StateTable.Item(subjectID)
            Dim socket As Socket = oldState.workSocket
            If Not (socket Is Nothing) Then
                socket.Shutdown(SocketShutdown.Both)
                socket.Close()
            End If

            StateTable.Remove(subjectID)
        End If
        StateTable.Add(subjectID, state)
    End Sub 'updateStateTable

    Private Sub ReSendMessage(ByVal subjectID As Integer)
        Dim state As ExpStateObject = StateTable.Item(subjectID)
        Dim msg As MQMessage

        Dim i As Integer
        SyncLock (state)
            For i = 0 To state.MessageQueue.Count
                msg = state.MessageQueue.Item(i)
                state.workSocket.Send(msg.toBytes)
            Next
        End SyncLock

    End Sub

    Private Sub Send(ByVal handler As ExpStateObject, ByVal data As MQMessage)
       'Dim byteData As Byte() = SerializeUtils.Serialize(data)
        SyncLock (handler)
            handler.MessageQueue.Add(data)
            Dim message() As Byte = data.toBytes

            handler.workSocket.Send(message)

        End SyncLock
    End Sub 'Send

    Public Sub startExperiment()
        isExperimentStart = True
    End Sub