7

I have found this piece of code on the internet: it does not open a server listening on port 11000, as I hoped.

What can be the problem? I normally code in Delphi, so I am little lost. I have made a corresponding client in Delphi, which works.

I am using demo version of C# 2015.

    public static void StartListening()
    {
        // Data buffer for incoming data.
        byte[] bytes = new Byte[1024];

        // Establish the local endpoint for the socket.
        // Dns.GetHostName returns the name of the 
        // host running the application.
        IPHostEntry ipHostInfo = Dns.Resolve(Dns.GetHostName());
        IPAddress ipAddress = ipHostInfo.AddressList[0];
        IPEndPoint localEndPoint = new IPEndPoint(ipAddress, 11000);

        // Create a TCP/IP socket.
        Socket listener = new Socket(AddressFamily.InterNetwork,
            SocketType.Stream, ProtocolType.Tcp);

        // Bind the socket to the local endpoint and 
        // listen for incoming connections.
        try
        {
            listener.Bind(localEndPoint);
            listener.Listen(10);

            // Start listening for connections.
            while (true)
            {
                //Console.WriteLine("Waiting for a connection...");
                // Program is suspended while waiting for an incoming connection.
                Socket handler = listener.Accept();
                data = null;

                // An incoming connection needs to be processed.
                while (true)
                {
                    bytes = new byte[1024];
                    int bytesRec = handler.Receive(bytes);
                    data += Encoding.ASCII.GetString(bytes, 0, bytesRec);
                    if (data.IndexOf("#") > -1)
                    {
                        break;
                    }
                }

                // Show the data on the console.
                //Console.WriteLine("Text received : {0}", data);

                // Echo the data back to the client.
                byte[] msg = Encoding.ASCII.GetBytes(data);

                handler.Send(msg);
                handler.Shutdown(SocketShutdown.Both);
                handler.Close();
            }

        }
        catch (Exception e)
        {
            Console.WriteLine(e.ToString());
        }

        //Console.WriteLine("\nPress ENTER to continue...");
        //Console.Read();

    }
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2
  • What is the exception from bind? Commented Sep 19, 2016 at 12:29
  • Thank you very much. No exception on bind. Commented Sep 26, 2016 at 6:10

3 Answers 3

Reset to default
9

The problem might be here: Whats the IP address of ipHostInfo.AddressList[0] ? It might be the loop-back. I never restrict my server endpoint to an ip-adress unless I need to, but then I will specify it in a configfile.

IPEndPoint localEndPoint = new IPEndPoint(IPAddress.Any, 11000);
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1 Comment

That was the problem, exactly, Thank you very much.
1

As per Jeroen's answer, encountered per .NET's Synchronous Server Socket Example. When listening/connecting to localhost, one should rather use

IPAddress ipAddress = IPAddress.Parse("127.0.0.1");

instead of

// Establish the local endpoint for the socket.  
// Dns.GetHostName returns the name of the   
// host running the application.  
IPHostEntry ipHostInfo = Dns.GetHostEntry(Dns.GetHostName());  
IPAddress ipAddress = ipHostInfo.AddressList[0];
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0

Thanks for feedback. I found som other, older code:

TcpListener serverSocket = new TcpListener(11000);

that does the job. I know it is depreciated, but it works, actually.

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1 Comment

If you take a look into the code you'll see it does exactly the same as @Jeroen mentioned in his answer. So you should at least upvote his answer and/or accept it.

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