vb.net 2010套接字突然停止？

Question

I am currently creating a multi-client server application in vb.net 2010. I am using sockets and network streams to read the data.

it's hard to explain what is happening and posting code probably won't do much good being the scale of my project. However, i'll just give a run through of what i am doing and then what happens and hopefully someone can help me, or give me some ideas on what could be happening :).

I start up the server and client and they both connect and listen asynchronously. In my client, i put in the login information and send it to the server using the network stream. The server reads everything fine, starts listening again, handles the data, sends account information to client, says the client is connected, and then randomly closes once it's done handling the data and exits the function. While this is happening, the client is receiving the data, starts listening again, handles the data, says the socket is connected, and then once everything is done, randomly closes after the function is done.

Now I have already made sure that other code wasn't affecting the sockets, and commented everything out that wasn't needed and would allow each the server and client to keep looping. (creating a game so there's a serverloop and gameloop) It just seems like it does all the work and then exits out the reading sub, and just stops listening for more to read.

If anyone has any idea's it would be greatly appreciated. Thanks in advance!

The code is the same on each side:

Receiving data:

    Private Sub ReceiveOneByte(ByVal ar As IAsyncResult)
    Dim netStream As NetworkStream
    Dim InData() As Byte
    Dim DataLen(3) As Byte
    Dim inLength As Integer
    Dim Buffer As New clsBuffer
    Dim MsgType As Integer
    Dim NewData() As Byte
    Dim Empty() As Byte

    SyncLock Client_TCP.Client
        Try
            netStream = New NetworkStream(Client_TCP.Client)
        Catch ex As Exception
        End Try
        ' gets length of data comming in
        Try
            netStream.Read(DataLen, 0, 4)
        Catch ex As Exception
        End Try
        inLength = BitConverter.ToInt32(DataLen, 0)

        ' gets data comming in
        ReDim InData(inLength)
        netStream.Read(InData, 0, inLength)
        netStream.Flush()
    End SyncLock

    Buffer.WriteBytes(InData)
    MsgType = Buffer.ReadLong

    If InData.Length > (InData.Length - 4) Then
        ReDim NewData(InData.Length - 5)
        Array.ConstrainedCopy(InData, 4, NewData, 0, NewData.Length - 1)
        HandleDataSub(MsgType)(0, NewData)
    Else
        HandleDataSub(MsgType)(0, Empty)
    End If

    Client_TCP.GetStream.BeginRead(Readbyte, 0, 1, New AsyncCallback(AddressOf ReceiveOneByte), Nothing)

End Sub

To Send Data:

    Public Sub Send(ByVal Data() As Byte)
    Dim netStream As NetworkStream
    Dim len As Integer = Data.Length
    Dim DataLen() As Byte = BitConverter.GetBytes(len)
    Dim bit(0) As Byte
    bit(0) = 1
    SyncLock Client_TCP.Client
        netStream = New NetworkStream(Client_TCP.Client)
        netStream.Write(bit, 0, 1)
        netStream.Write(DataLen, 0, 4)
        netStream.Write(Data, 0, Data.Length)
        'netStream.Flush()
    End SyncLock
End Sub

Answer 1

When you use the IAsyncResult Begin*(...) pattern, it is required that you call the End*(...) method. This is the place where it will tell you about any problems it had. It is probably trying really hard to tell you what the problem is, but you aren't checking. Incidentally, in this particular case this is also where you can check the number of bytes returned - it could be 0 if the stream terminated unexpectedly. So the first thing to add at the top of your method is (pseudocode... ok, who am I kidding... C#):

try {
    int bytesRead = Client_TCP.GetStream.EndRead(ar);
    if(bytesRead < 1) {
        // EOF; do something
    } else if(bytesRead == 1) {
        // this is your expected scenario: your code here
    } else {
        // well that's just crazy talk!
    }
} catch (Exception ex) {
    // log this exception; shouldn't throw, because you are on a worker
    // thread here; you *might* want to clean up, though
}

This will probably get you started on diagnosing the problem. It should also be noted that this is not the most efficient way to use a socket - but it should work, and I don't want to confuse things by start talking about alternative async APIs etc.