Asynchronous vs. Synchronous socket server for real-time application

I am currently developing a C# socket server that needs to send and receive commands to a real-time process. The client is an android device. Currently the real-time requirements are "soft", however in the future more strict timing requirements might arise. Lets say in the future it might be to send commands to a crane that could be potentially dangerous.

The server is working, and seemingly very well with my current synchronous socket server design. I have separate threads for receiving and sending data. I am wondering if there would be any reason to attempt an asynchronous server socket approach? Could it provide more stability a开发者_高级运维nd/or faster performance?

I'll gloss over the definition of real time and say that asynchronous sockets won't make the body of the request process any faster, but will increase concurrency (the number of requests you can take at any one time). If all processors are busy processing something, you won't get any gain. This only gives you gain in the situation where a processor would have sat waiting for a socket to receive something.

Just a note on real time, if your real time requirements are anything like the need to guarantee a response in x-time, then C# and .NET will not give you such guarantees. This, however, depends on your current and future definitions of "soft". It may be the case that you happen to be getting good response times, but don't confuse that with true real time systems.

If you're doubting the usefullness of something asynchronous in your aplications then you should definitely read about this. It gives you a clear idea of what the asynchronous solutions could add to your applications

I don't think you are going to get more stability or faster performance. If it really is a "real-time" system, then it should be synchronous. If you can tolerate "near real-time" and there are long running or expensive compute operations, then you could consider an asynchronous approach. I would not add the complexity if not needed though.

If it's real time, then you absolutely want your communications to be backed by a queue so that you can prove temporal logic on that queue. This is what nio/io-completion-ports/async gives you. If you are using synchronous programming then you are wasting your CPU while copying data from RAM to the network card.

Furthermore, it means that your server is absolutely single-threaded. You may have a single thread even with async, but still be able to serve thousands of requests.

Say for example that a client wanted to perform a DOS attack. He would connect and send one byte of data. Your application would now become unable to receive further commands for the timeout of that connection, which could be quite large. With async, you would ACK the SYN package back, but your code would not be waiting for the full transmission.