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    <p>Your solution is quite OK for many cases when the number of connected clients is small compared to the performance of the enumerating the collection of their contexts. If you allow some wiggle room in the timeout (i.e. it's OK to disconnect the client somewhere between 55 and 65 seconds of inactivity), I'd just run the purging routine every so often.</p> <p>The other approach which worked great for me was using a queue of activity tokens. Lets use C#:</p> <pre><code>class token { ClientContext theClient; // this is the client we've observed activity on DateTime theTime; // this is the time of observed activity }; class ClientContext { // ... what you need to know about the client DateTime lastActivity; // the time the last activity happened on this client } </code></pre> <p>Every time an activity happens on a particular client, a token is generated and pushed into FIFO queue and <code>lastActivity</code> is updated in the <code>ClientContext</code>.</p> <p>There is another thread which runs the following loop:</p> <ul> <li>extracts the oldest token from the FIFO queue;</li> <li>checks if <code>theTime</code> in this token matches the <code>theClient.lastActivity</code>;</li> <li>if it does, shuts down the client;</li> <li>looks at the next oldest token in the queue, calculates how much time is left till it needs to be shutdown;</li> <li><code>Thread.Sleep(&lt;this time&gt;)</code>;</li> <li>repeat</li> </ul> <p>The price of this approach is a little, but constant, i.e. O(1) overhead. One can come up with faster best case solutions, but it seems to me that it's hard to come up with a one with faster worst case performance.</p>
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    1. POHandling Timeouts in a Socket Server
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    1. USRom
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    1. COwouldn't there still be a lock on that FIFO queue each time i updated it or whenever i loop it? updating the last activity of each client is not a problem - my client connection wrapper automatically does that whenever there is activity. the problem is when i loop this FIFO queue (or any collection for that matter), i need to lock it while processing it. or maybe i'm just misunderstanding something here...
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    2. CO@shyneman: locking a queue with multiple writers and one reader is a very simple proposition. Even if you lock the whole queue (there are better solutions, but lets assume the worst: locking the whole queue), pushing and pulling items into/from the queue is a very cheap operation. You don't need to enumerate the queue: just push and pull. But in reality this is one of the classic uses of lock-free queues: there are plenty of implementations on the web.
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