Exception in socket acceptor thread crashing the whole application

[RemiGaudin]

This issue looks similar than #257 but this one is on the acceptor side, more precisely in the ThreadedSocketReactor.Run() function.

If any exception occurs while calling tcpListener_.Start() in ThreadedSocketReactor.Run(), then the whole application is crashing as there is no try/catch and the function runs on a dedicated thread. Typically an exception would occur here when the port is already in use by another application, thus the issue is easy to reproduce.

I would be glad to provide a fix via a PR but before that I would like some advice about the best way to fix it. In my opinion this is not enough to just silently catch tcpListener_.Start(), we should also notify the parent application in some way otherwise it won't know that the acceptor did not start successfully. With that in mind I see two different approaches:

1. We simply move tcpListener_.Start() from the Run() function to the Start() one, so in case of exception the parent application will be able to catch it and thus will be notified about the failure. For now the only thing the Start() function is doing is starting the Run() one on a different thread, where tcpListener_.Start() will immediately be called. So this change would break a little bit the asynchronicity of the Start() function but it seems quite harmless to me.
2. We add a try/catch block in the Run() function, but then we need to find a way to notify the parent application about the exception. My first suggestion would be to create a new event including the error message than the ThreadedSocketReactor would raise, then the ThreadedSocketAcceptor would relay, so the parent application would be able to listen to it.

There's certainly other ways to fix that so I'm open to any ideas.

[ajk002]

Hi, I am finding a similar situation where a socket exception is bringing down the entire application. Any recommended resolution for this ?

[KieranBond]

Hey.

My team and I are also facing this issue - We can't catch the Port already being used as no Error gets thrown up to us and so this causes our whole application to crash at some point soon after.

[KieranBond]

@gbirchmeier just wanting to float this to the top of the pile

[gbirchmeier]

Commening here only to acknowledge this issue.

I'm not sure which of @RemiGaudin 's solutions would be better. I agree that his option (1) doesn't seem disruptive-- in fact, it cuts out a lock call which could possibly be beneficial in theory (but realistically probably not).

[gbirchmeier]

Is there an easy-ish way to force the _tcpListener.Start exception and cause this issue to occur?