Cannot write to closed socket

[ElPresidente408]

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

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

    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

    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.