Cannot write to closed socket

I want to start by saying I've read dozens of tutorials on chat programs, except everyone does it differently and now I'm a little confused. I think I have this right, but input is greatly appreciated.

I'm making a small, direct chat program which only chats with another computer. The stream is encrypted using CryptoStream. My problem is that my CryptoStream won't send the message unless I use .Close(), but then that closes the socket. So my first message will be received, but the second message throws an error.

I should say under my current code, the chat works fine using .Flush() on the network stream itself if I take CryptoStream completely out of the picture.

When I create my class, it starts a new thread which will do the listening

Code:

---

    Public Sub New(ByVal Key As String)
        MyBase.New()
        readThread = New System.Threading.Thread(AddressOf ReadMessage)
        readThread.IsBackground = True
        readThread.Start()
End Sub

---

Code:

---

    Private Sub ReadMessage()
        Dim TCPinbound As TcpClient
        Dim listener As New TcpListener(Net.IPAddress.Any, 12345)
        listener.Start()

        Do While True
            Dim IncomingMsg As String
            TCPinbound = listener.AcceptTcpClient

            Dim DecryptStream As New CryptoStream(TCPinbound.GetStream(), RMCrypto.CreateDecryptor(Password, IV), CryptoStreamMode.Read)
            Dim reader As New IO.StreamReader(DecryptStream)
            IncomingMsg = reader.ReadToEnd

            If Not IncomingMsg = Nothing Then
                RaiseEvent TransmissionRecieved(IncomingMsg)
            End If
        Loop
    End Sub

---

This is my code for sending

Code:

---

    Public Sub ConnectToClient(ByVal HostName As String)
        TCPoutbound = New TcpClient(HostName, 12345)
    End Sub

    Public Sub SendMessage(ByVal str As String)
        CryptStream = New CryptoStream(TCPoutbound.GetStream, RMCrypto.CreateEncryptor(Password, IV), CryptoStreamMode.Write)

        Dim output() As Byte = Encoding.ASCII.GetBytes(str)
        CryptStream.Write(output, 0, output.Length)
        CryptStream.Flush()
        CryptStream.FlushFinalBlock()
        CryptStream.Close()

    End Sub

---

Those last three lines written as such will successfully send one message. Trying to send a second says the socket is closed. Removing the .Close() prevents anything from being sent, until I quit my application and then a stream is received one final time.

Just a stab, instead of those last 3 methods have you tried using .Dispose instead after the Write method?

Quote:

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Originally Posted by dee-u

Just a stab, instead of those last 3 methods have you tried using .Dispose instead after the Write method?

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I think I found the source of my problem. It explains why this doesn't work with cryptostream. This was posted on codeproject:
http://www.codeproject.com/KB/IP/RCS...?display=Print


So, the problem is, the NetworkStream is a byte stream while the CryptoStream is a block stream. As such, you can't connect the two because the NetworkStream never tells the CryptoStream that it has read the last byte of the last block. However, if you use an intermediate MemoryStream, then everything works well, at the sacrifice of having to buffer the entire packet in memory before shipping it off the NetworkStream. That may be a big sacrifice, however, it's the implementation I chose to illustrate in this article.

I'm just trying to understand how the memorystream step works