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    <p>Using <code>Thread.Sleep</code> outside of test code is generally not ideal.</p> <p>You can use <code>System.Threading.Timer</code> objects for both these requirements.</p> <hr> <p><strong>EDIT</strong> if you want to prevent concurrent calls, you can use a lock to implement mutual exclusion.</p> <p>Create an object to lock on that can be seen by both timer handlers:</p> <pre><code>public object gate = new object(); </code></pre> <hr> <p>For the polling, you want to set up a timer like this:</p> <pre><code>var pollTimer = new Timer( HandlePoll, null, 0, Timeout.Infinite ); ... void HandlePoll( object state ) { lock ( gate ) { DoPoll(); } pollTimer.Change( pollInterval, Timeout.Infinite ); } </code></pre> <p>I've set the period to <code>Timeout.Infinte</code> so the timer doesn't repeat. This means <code>pollInterval</code> is the time between one poll finishing and another starting - which will be different to the poll period if <code>DoPoll()</code> takes some time.</p> <p>Doing it this way also prevents the timer ticking again while a previous poll is still running.</p> <hr> <p>You can use the same principal to send the commands, but you will have to manage the current index into the <code>sequencesList</code>:</p> <pre><code>var seqTimer = new Timer( HandleSequence, null, 0, Timeout.Infinate ); int seqIndex = 0; ... void HandleSequence( object state ) { var opcode = sequencesList[sequenceName][ seqIndex ]; byte register = opcode.register; bool bit = opcode.bit; int duration = opcode.duration; lock( gate ) { SetRegister(register, bit, false); } seqIndex++; if ( seqIndex &lt; sequencesList[sequenceName].Count ) { seqTimer.Change( duration, Timeout.Infinte ); } } </code></pre> <p>Or something along those lines ( but with suitable error handling! )</p> <p>You can handle termination and cancellation by just disposing the timers.</p> <hr> <p>BTW, there is an excellent ( and free ) ebook about threading that you could read:</p> <p><a href="http://www.albahari.com/threading/" rel="nofollow"><code>Albahari: Threading in C#</code></a></p>
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    1. COThanks for your code. Tried your method, but still I'm facing problems with synchronization. Seems like in case I'm sending one message to the controller while still haven't got an answer for a previous message, its crushes. The exception is: `The I/O operation has been aborted because of either a thread exit or an application request.`
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    2. CO@toy4fun I've added mutual exclusion to my answer.
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    3. COIt's working perfectly now. I've tried the same `Lock()` mechanism with the 2 BackgroundWorkers solution and it also works. I just need to decide which solution is considered as best practice - BackgroundWorkers vs. Timers. Thanks again.
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