TcpListener Freeze Problem

I am creating a TCP Listener and listener and I am using the code from the MSDN pages located here:

For some reason I am having a problem with the listener code freezing up on me. Does anyone know what might be causing this?

Here is the Listener:

Code:

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Class MyTcpListener

    Public Shared Sub Main()

        Dim server As TcpListener
        server = Nothing
        Try
            ' Set the TcpListener on port 13000.
            Dim port As Int32 = 13000
            Dim localAddr As IPAddress = IPAddress.Parse("127.0.0.1")

            server = New TcpListener(localAddr, port)

            ' Start listening for client requests.
            server.Start()

            ' Buffer for reading data
            Dim bytes(1024) As Byte
            Dim data As String = Nothing

            ' Enter the listening loop.
            While True
                Form2.TextBox2.Text = "Waiting for a connection... "

                ' Perform a blocking call to accept requests.
                ' You could also user server.AcceptSocket() here.
                Dim client As TcpClient = server.AcceptTcpClient()
                Form2.TextBox2.Text = "Connected!"

                data = Nothing

                ' Get a stream object for reading and writing
                Dim stream As NetworkStream = client.GetStream()

                Dim i As Int32

                ' Loop to receive all the data sent by the client.
                i = stream.Read(bytes, 0, bytes.Length)
                While (i <> 0)
                    ' Translate data bytes to a ASCII string.
                    data = System.Text.Encoding.ASCII.GetString(bytes, 0, i)
                    Form2.TextBox2.Text = "Received: {0}" & data

                    ' Process the data sent by the client.
                    data = data.ToUpper()
                    Dim msg As Byte() = System.Text.Encoding.ASCII.GetBytes(data)

                    ' Send back a response.
                    stream.Write(msg, 0, msg.Length)
                    Form2.TextBox2.Text = "Sent: {0}" & data

                    i = stream.Read(bytes, 0, bytes.Length)

                End While

                ' Shutdown and end connection
                client.Close()
            End While
        Catch e As SocketException
            Console.WriteLine("SocketException: {0}", e)
        Finally
            server.Stop()
        End Try

        Console.WriteLine(ControlChars.Cr + "Hit enter to continue....")
        Console.Read()
    End Sub 'Main

End Class 'MyTcpListener

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Here is the Client:

Code:

---

Shared Sub Connect(ByVal server As [String], ByVal message As [String])
        Try
            ' Create a TcpClient.
            ' Note, for this client to work you need to have a TcpServer
            ' connected to the same address as specified by the server, port
            ' combination.
            Dim port As Int32 = 13000
            Dim client As New TcpClient(server, port)

            ' Translate the passed message into ASCII and store it as a Byte array.
            Dim data As [Byte]() = System.Text.Encoding.ASCII.GetBytes(message)

            ' Get a client stream for reading and writing.
            '  Stream stream = client.GetStream();
            Dim stream As NetworkStream = client.GetStream()

            ' Send the message to the connected TcpServer.
            stream.Write(data, 0, data.Length)

            Console.WriteLine("Sent: {0}", message)

            ' Receive the TcpServer.response.
            ' Buffer to store the response bytes.
            data = New [Byte](256) {}

            ' String to store the response ASCII representation.
            Dim responseData As [String] = [String].Empty

            ' Read the first batch of the TcpServer response bytes.
            Dim bytes As Int32 = stream.Read(data, 0, data.Length)
            responseData = System.Text.Encoding.ASCII.GetString(data, 0, bytes)
            Console.WriteLine("Received: {0}", responseData)

            ' Close everything.
            stream.Close()
            client.Close()
        Catch e As ArgumentNullException
            Console.WriteLine("ArgumentNullException: {0}", e)
        Catch e As SocketException
            Console.WriteLine("SocketException: {0}", e)
        End Try

        Console.WriteLine(ControlChars.Cr + " Press Enter to continue...")
        Console.Read()
    End Sub 'Connect

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The Exception I am getting is

Code:

---

A first chance exception of type 'System.Net.Sockets.SocketException' occurred in System.dll

---

Any other code you need just let me know. Thanks in advance for the replies.:)

What line does the debugger highlight when it throws the error?

I am not entirely sure but if you are executing on the same computer then the exception maybe because you are using the same port for those two applications?

MaximilianMayrhofer:

Strangely It doesn't highlight the line as it would for a normal exception, it just prints the error in the Immediate Window while debugging.

Here is the block of code in the tcplistener section that it shows the message on:

Code:

---

  Try
                Catch
                    Dim client As TcpClient = server.AcceptTcpClient()
                    Form2.TextBox2.Text = "Connected!"

---

dee-u

This could also be a possibility because I am testing it on the same computer. Unfortunately I do not have a second machine to test it on right now so any other suggestions or if you are sure this might be the problem, I really appreciate it. Thanks.

Could it be that the exception is written there since you are using this?

Code:

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Catch e As SocketException
            Console.WriteLine("SocketException: {0}", e)

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Hmm, Well that would seem logical. However, I am very new to network programming and only been in VB coding for around 1 year.

So, what would be the best method to fix this issue?

Oh I would also like to add that I am doing this all within one application. The listener and the client are just two different forms. Could this be why I am receiving an error?

Ideas anyone?:confused: