Pfthb

I have a server application with a socket listening:

server = new TcpListener(myEndPoint);

// etc.

socket = server.AcceptSocket();

while (true) 

 int size = socket.Receive(data); // application waits here for data.

 if (size == 0)
 
 // handle disconnect
 
 else
 
 // process data.
 

Now the client application connects to this...

var socket = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);

socket.Connect(remoteIp, remotePort);

sends the data, and when it's done it calls

socket.ShutDown(SocketShutdown.Both);

At this point, I'd expect the server, which was blocking at socket.Receive(data) to proceed, but with a size of 0.

as per this page:

https://docs.microsoft.com/en-us/dotnet/api/system.net.sockets.socket.receive?view=netframework-4.7.2

If the remote host shuts down the Socket connection with the Shutdown method, and all available data has been received, the Receive method will complete immediately and return zero bytes.

But it just waits here forever.

The funny thing is, if I connect to the server application with PuTTY, and then close PuTTY, then the Receive() method does complete and return with size = 0. What's PuTTY doing that I'm not?

Note: I've also tried using a TcpClient on the client application but this has the same problem.

Turns out it was my fault, I'll leave it here in case someone else has the same problem.

While trying Minu's suggestion I noticed that if I just closed the socket without having sent data, the Receive() completed correctly.

It turns out that elsewhere in my code, I had the server sending back an acknowledgement after receiving the completed data. However, the client's method to receive the acknowledgement had a bug in it that was causing it not to completely receive it from the socket and so there were still 7 bytes Available on the socket which is why it wasn't closing.