TCP Client Not Reconnecting After Disconnect

Question

I've made a server and a client. The client should re-attempt to connect to the server if I close the server. I've made it so when the try/catch during waitForCommands fails, it restarts the attemptConnection method in a new thread. The problem I have here is that it simply won't reconnect. As a test, I open my TCP server and the TCP client. The client connects to the server as usual. Then, I close the TCP Server, and the clients spits out this error: 'System.Net.Sockets.SocketException' rapidly, and never connects.

class Program
{
    public static TcpClient client = new TcpClient();
    public static NetworkStream stream;
    public static byte[] readBuffer;

    static void Main(string[] args)
    {
        new Thread(attemptConnection).Start();
    }

    public static void waitForCommands()
    {
        while (client.Connected)
        {
            try
            {
                readBuffer = new byte[client.ReceiveBufferSize];
                int data = stream.Read(readBuffer, 0, readBuffer.Length);
                string plainText = Encoding.ASCII.GetString(readBuffer, 0, data);
                if (plainText.Contains("mbox"))
                {
                    MessageBox.Show("");
                }
            }

            catch
            {
                new Thread(attemptConnection).Start();
            }

        }
    }

    public static void attemptConnection()
    {
        while(!client.Connected)
        {
            try
            {  
                client.Connect("127.0.0.1", 23154);
                stream = client.GetStream();
                new Thread(waitForCommands).Start();
            }

            catch(Exception ex)
            {
                Console.WriteLine(ex.Data);
            }
        }

    }
}

An interesting thing I noticed, is that if I write 'client.Close();' on the server exit event, I get no error messages when the client tries to reconnect. It just shows a blank screen and does nothing

If you'd like to see the code that waits for connections on my server, it's really simple so I'm not sure why this problem is occuring.

    public static void waitForConnection()
    {
        server.Start();
        client = server.AcceptTcpClient();
        stream = client.GetStream();
        f.labelControl1.Text = "Connected";
    }

You have to assign a new TcpClient instance to your client variable. — Jasper Catthoor, Jan 15 '17 at 21:34

score 2 · Accepted Answer · edited May 23 '17 at 11:45

To expand on my comment, I think it's due to the underlying TCP connection (the network stream) not closing automatically.

Try closing the stream manually and see what it does:

client.GetStream().Close();

You could also just close the client which closes the stream for you (see https://msdn.microsoft.com/en-us/library/system.net.sockets.tcpclient.close.aspx):

client.Close();

And another way to resolve your issue (see https://stackoverflow.com/a/38006848/4408417):

client.Client.Disconnect(true);

score 1 · Answer 2 · answered Jan 16 '17 at 00:17

1

I changed client.Connect() to

client = new TcpClient();
client.Connect("127.0.0.1", 23154);

As Jasper recommended in the comments

answered Jan 16 '17 at 00:17

rrrrrrrrrrrrrrrr

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TCP Client Not Reconnecting After Disconnect

2 Answers2