Check socket status before writing handshake response (may fix #74)

[nicokaiser]

I still don't get it, but my server ran into this if-statement twice this day, when it would otherwise crash because of #74.

[nicokaiser]

Ok without this patch I get occasional "Error: EPIPE" crashes in the application (as the "write" happens before the application gets the chance to add an error handler).

When the socket is writable, either the write succeeds, or it fails, but at a time when there is either an error handler (the applications can set one immediately after the handshake) or the connection is already destroyed (invalid handshake, etc.).

[nicokaiser]

Ok, but I'm still getting "Error: EPIPE" crashes.

[nicokaiser]

@einaros You seem to remove all(!) listeners from the socket after closing (in cleanupWebsocketResources), even the default error handler that just destroys the socket. This may cause my occasional EPIPE errors...

Perhaps (!) this fixes that:
https://github.com/nicokaiser/ws/commit/f5c31d10a69c7075776c3165446adc8cf110472c

I'll try for a few hours and see if it crashes again...

[einaros]

Ah, yeah. I'll complete my fixes on this tonight, and include that patch as well. Sorry for the long delay!

[einaros]

I manually included updates which resemble the ones you've included here. Could your setup to master and see if stability improves?

[einaros]

Closing this - let's reiterate if the current fixes aren't sufficient :)