C#: How do I terminate a socket before Socket.BeginReceive calls back?

Question

I have a server that receives connection requests from clients. This server makes use of the asynchronous Socket.BeginReceive and Socket.EndReceive method. The code is pretty similar to the code found here.

In my case, after calling Socket.BeginReceive I need a timeout such that if the client hangs on to the connection but does not transmit any data at all for a fixed amount of time, I need to terminate the connection.

• How do I go about terminating the connection in this scenario?
• What is the best way of coding a timer?

Answer 1

According to the MSDN article on Socket.BeginReceive it states

To cancel a pending BeginReceive, call the Close method.

Answer 2

You can Receive some initial data asynchronously and then make synchronous Receive for rest of the data and rely on ReceiveTimeout to disconnect the client. You can use Socket.Close to forcefully disconnect client.

But if you want to use async Receive only, then you can use timers and reset them on EndReceive. If it elapse you can disconnect the client forcefully.

But I think the first approach is better.

Answer 3

Just call the socket's Close() method. The callback method will run pretty quickly after that, you'll get an ObjectDisposedException when you call the EndReceive() method. Be prepared to catch that exception.

You probably don't want to block the thread that called BeginReceive, you'll need a System.Threading.Timer or System.Timers.Timer to detect the timeout. Its callback should call Close(). Beware of the inevitable race-condition this causes, the timer's callback will run if the response was received a microsecond before the timer expired. You'll close the socket, even though you got a good response. The next call to BeginReceive() will fail immediately.