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copied!<p>Microsoft has a nice async TCP server example. It takes a bit to wrap your head around it. It was a few hours of my own time before I was able to create the basic TCP framework for my own program based on this example.</p> <p><a href="http://msdn.microsoft.com/en-us/library/fx6588te.aspx" rel="nofollow">http://msdn.microsoft.com/en-us/library/fx6588te.aspx</a></p> <p>The program logic goes kind of like this. There is one thread that calls listener.BeginAccept and then blocks on allDone.WaitOne. The BeginAccept is an async call which gets offloaded to the threadpool and handled by the OS. When a new connection comes in, the OS calls the callback method passed in from BeginAccept. That method flips allDone to let the main listening thread to know it can listen once again. The callback method is just a transitionary method and continues on to call yet another async call to receive data. </p> <p>The callback method supplied, ReadCallback, is the primary work "loop"(effectively recursive async calls) for the async calls. I use the term "loop" loosely because each method calls actually finishes, but not before calling the next async method. Effectively, you have a bunch of async calls all calling each other and you pass around your "state" object. This object is your own object and you can do whatever you want with it. </p> <p>Every callback method will only get two things returned when the OS calls your method:</p> <p>1) Socket Object representing the connection </p> <p>2) State object with which you use for your logic</p> <p>With your state object and socket object, you can effectively handle your "connections" asynchronously. The OS is VERY good at this.</p> <p>Also, because your main loop blocks waiting for a connection to come it and off-loads those connections to the thread pool via async calls, it remains idle most of the time. The thread pool for your sockets is handled by the OS via completion ports, so they don't do any real work until data comes in. Very little CPU is used and it's effectively threaded via the thread pool.</p> <p>P.S. From what I understand, you don't want to do any hard work with these methods, just handling the movement of the data. Since the thread pool is the pool for your Network IO and is shared by other programs, you should offload any hard work via threads/tasks/async as to not cause the socket thread pool to get bogged down.</p> <p>P.P.S. I haven't found a way of closing the listening connection other than just disposing "listener". Because the async call for beginListen is called, that method will never return until a connection comes in, which means, I can't tell it to stop until it returns. I think I'll post a question on MSDN about it. and link if I get a good response.</p>

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