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POHow do you close TCP connections gracefully without exceptions?
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copied!<p>What is the pattern and/or how would you change the following code so that a connection can be closed gracefully from either server or client, without needing exception handling.</p> <ol> <li><p><strong>TcpClient vs. Socket:</strong> I'm not tied to using the TcpClient client class. I wrote the following code to try to demonstrate the simplest case possible. I had been using a Socket & SocketAsyncEventArgs but things were getting too complicated dealing with this issue. </p></li> <li><p><strong>Blocking vs. Asynchronous:</strong> Because of the blocking calls this may be difficult or impossible. If so, that's fine, but how do you solve it in the asynchronous case?</p></li> <li><p><strong>Quit Token?:</strong> I've experimented with sending some kind of "Quit" token to other side so that it knows to shutdown, but haven't gotten it working and I wanted to present a minimal example here. </p></li> <li><p><strong>Exception Handling Needed Anyways:</strong> I know exception handling will be necessary in the <em>real</em> application as network connections etc will fail. But can not the <strong>expected</strong> case of a graceful shutdown be handled without exceptions??</p></li> </ol> <p><strong>Edit:</strong> I moved original and answer code to <a href="https://gist.github.com/958955" rel="nofollow noreferrer">gist</a>. </p> <p><strong>Original <em>failing</em> Example</strong>: Moved to here: <a href="https://gist.github.com/958955#file_original.cs" rel="nofollow noreferrer">https://gist.github.com/958955#file_original.cs</a></p> <p><strong>Current Working Answer</strong>: <a href="https://gist.github.com/958955#file_answer.cs" rel="nofollow noreferrer">https://gist.github.com/958955#file_answer.cs</a></p> <pre><code>class Channel { private readonly TcpClient client; private readonly NetworkStream stream; private readonly string name; private readonly ManualResetEvent quit = new ManualResetEvent(false); public Channel(string name, TcpClient client) { this.name = name; this.client = client; stream = client.GetStream(); } public void Run() { Console.WriteLine(name + ": connected"); byte[] buffer = new byte[client.Client.ReceiveBufferSize]; stream.BeginRead(buffer, 0, buffer.Length, this.Read, buffer); var writer = new StreamWriter(stream, Encoding.ASCII); while (true) { var line = Console.ReadLine(); if (String.IsNullOrEmpty(line) || !this.client.Connected) break; writer.WriteLine(line); writer.Flush(); } if (client.Connected) { Console.WriteLine(name + " shutting down send."); client.Client.Shutdown(SocketShutdown.Send); Console.WriteLine(name + " waiting for read to quit."); quit.WaitOne(); } else { Console.WriteLine(name + " socket already closed"); } Console.WriteLine(name + " quit, press key to exit."); Console.ReadKey(); } private void Read(IAsyncResult result) { var bytesRead = this.stream.EndRead(result); if (bytesRead == 0) { Console.WriteLine(name + " read stopped, closing socket."); this.client.Close(); this.quit.Set(); return; } var buffer = (byte[])result.AsyncState; Console.WriteLine(name + " recieved:" + Encoding.ASCII.GetString((byte[])result.AsyncState, 0, bytesRead)); stream.BeginRead(buffer, 0, buffer.Length, this.Read, buffer); } } </code></pre>

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