How detect whet client disconnected

[ahvahsky2008]

When user connected to socket - i add data to db. I want delete this data when user is disconnected. How detect when connection is closed?

[asergeyev]

Process could handle "input closed", so where you read input you should have some sort of idea that client is no longer there.. Next step is handling SIGINT (unless you're on windows). You could catch it and do what your script needs for a cleanup. Next is SIGTERM but I would not recommend to perform any action there as you have two earlier opportunities that sound better.

Note that if you choose SIGINT route you should fit your actions in 100ms to quit avoid SIGTERM. If you could not fit into that time you should use --closems to add certain number of milliseconds to that period.

[ahvahsky2008]

Can you share some examples ? I have more 5 years c# developing, but I don't understand what you mean

[asergeyev]

I have no idea about C# and how to do it there. I suppose to catch end of input you wrap your Console.ReadLine into try block and catch IOException later.

As signals go Windows is odd and I could not find any good example that I strongly feel works. Maybe someone else would mention way to do that.

[ahvahsky2008]

What about python script?

[asergeyev]

I'd hope readline will throw exception on reading from closed stdin and so you can use it as "disconnect" event. But no, it's not that simple :))) Python returns empty line in readline so we need something like this for our "greeter" example:

diff --git a/examples/python/greeter.py b/examples/python/greeter.py
index dddf24e..6dcde01 100755
--- a/examples/python/greeter.py
+++ b/examples/python/greeter.py
@@ -9,6 +9,11 @@ from sys import stdin, stdout

 # For each line FOO received on STDIN, respond with "Hello FOO!".
 while True:
-  line = stdin.readline().strip()
-  print('Hello %s!' % line)
+  line = stdin.readline()
+  if line == '':
+    break
+  print('Hello %s!' % line.strip())
   stdout.flush() # Remember to flush
+
+
+# cleanup here, client disconnected

Hope it makes sense