TCP Connections dropped after approx 5 mins of inactivity

Mike Taylor 116 Reputation points
2020-11-05T10:30:16.17+00:00

I have the idle timeout set to 20 minutes. However, tests with a Python TCP client talking to a a Python TCP server using "epoll", give me an issue when the idle time is roughly 5 minutes of inactivity. I loose the last packet sent, and get an error thrown from the client when after 10 minutes it tries to close the connection, as follows:-

Traceback (most recent call last):
File "atlas_client.py", line 121, in <module>
make_connection()
File "atlas_client.py", line 111, in make_connection
skt.shutdown(socket.SHUT_RDWR)
OSError: [Errno 107] Transport endpoint is not connected

Running this test locally on my Ubuntu VM, gives no such issue.

I am a bit of a loss as to what to try. I can (I believe) force keep-alive packets, however on a 4g connection when we are paying for each and every byte sent/received I don't really want to do this.

How can I tell whether this is an Azure firewall issue, Ubuntu VM or a problem with my code?

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Accepted answer
  1. Mike Taylor 116 Reputation points
    2020-11-16T19:17:57.58+00:00

    That's ok thank you, I have asked the question via Azure portal.

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  1. Mike Taylor 116 Reputation points
    2020-11-12T12:25:55.29+00:00

    @SaiKishor-MSFT

    Both side were done simultaneously, but to be sure I have redone them again and uploaded to the same place as before.

    Here is a guide to to the timeline:-
    11:56:00 Server was started
    11:57:00 Client was started (Pkt No 1 in client trace)
    11:57:17 Client sends first packet (Pkt No 4 in client trace, Pkt No 6 in server trace)
    12:02:17 Client (attempts) sends second packet (Pkt No 8 in client trace, Nothing in server trace)
    12:02:36 Client gives up and closes the connection (Pkt No 10 in client trace, Nothing in server trace)
    12:06:20 Server was stopped (Pkt No 10 in server trace).

    The reason you don't see the server send a RST is the connection has already been broken?

    Sub Id is 48dfe72b-8506-4366-9425-869bd1f64cef

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