Socket server stops accepting connections after a period of time

Question

We have an async socket server written in C#. (running on Windows Web Server 2008)

It works flawlessly up until it stop accepting new connections for an unknown reason.

We have about 200 concurrent connections on average, however we keep a count of both connections created and connections dropped. These figures can reach as high as 10,000 or as low as only 1000 before it just stops! It can run for up to around 8 hours sometimes before it stops or it can run for about half hour, at the moment it's running for about an hour before we have another application bring it back up automatically when that can't connect (not exactly ideal).

It doesn't appear like we're running out of sockets as we're closing them properly, we're also logging all errors and nothing is happening immediately before it stops.

We can figure this out. Does anyone have any ideas what might be going on?

I can paste code, but it generally just the same old async beginaccept/send code you see everywhere.

Answer 1

Without seeing code, it is almost imposible to wage a guess. But I'll try anyway, one thing that comes to mind is that you might not be maintaining a reference to the listening socket and at some point the GC collects the socket and your listening stops.

Now of course the fact that this sometime runs for hours makes this an almost unlikely reason, it is one that came to minds and thought worth mentioning.

Answer 2

Who initiates the active close, the client or the server? If it's the server then you may be accumulating socket's in TIME_WAIT state on the server and this may prevent you from accepting new connections. This is more likely if the client connections can be short lived and you go through periods when lots of short lived client connections occur.

Oh and if you ARE accumulating socket's in TIME_WAIT then please don't just assume that changing the machine-wide time wait period length is the best or only solution.