Client disconnects after some time if he is not in the same network

[jchristn]

Client disconnects after some time if he is not in the same network

[jchristn]

Hi, you may have to build a method that periodically sends a heartbeat message. I haven't found TCP keepalives to be completely reliable on all platforms, especially when there may be intermediary devices.

What OS are you using for client and server? Which framework/runtime are you using?

[w123u567]

Hi, you may have to build a method that periodically sends a heartbeat message. I haven't found TCP keepalives to be completely reliable on all platforms, especially when there may be intermediary devices.

What OS are you using for client and server? Which framework/runtime are you using?

I'm using Windows for server and client. The Server is a Windows Forms App (.Net Framework 4.7.2), the Client is a WPF Application (also .Net Framework 4.7.2)

[w123u567]

How often should this heartbeat method been called? I have a method on server that send all 50ms data to all clients and also a method on client site that sends all 50ms data to the server (if something changed)

[jchristn]

Hi @w123u567 I would start with something around 10 seconds. An alternative would be to use Wireshark on the client and server and see if a TCP reset is being sent from one side to the other, or from an intermediary device. Cheers, Joel

[w123u567]

Thank you, I will try this.

[w123u567]

Wireshark shows the following output:

It seems like the server sends a TCP reset to the client, but I don't understand why.

[w123u567]

I also implemented a method that sends every few seconds data (on client and on server), but nothing changed.

[jchristn]

Could you try setting _server.Keepalive.EnableTcpKeepAlives = false; and the same thing on the client, and see what happens? All of the TCP keepalive functionality is buried within the kernel - the properties I provide simply set them using the exposed APIs, and anecdotally, they aren't the most reliable.

[jchristn]

Also the 'spurious retransmissions' may be of concern - it indicates that Wireshark has already seen the ACK, but perhaps the ACK was not received by the sender.

Are your client and server on the same LAN segment, i.e. there's no router in between them (other than perhaps a WiFi router)?

https://www.chappell-university.com/post/spurious-retransmissions-a-concern

[w123u567]

Could you try setting _server.Keepalive.EnableTcpKeepAlives = false; and the same thing on the client, and see what happens? All of the TCP keepalive functionality is buried within the kernel - the properties I provide simply set them using the exposed APIs, and anecdotally, they aren't the most reliable.

I tried this and at the moment it's running since a few minutes without disconnecting. Maybe this was the solution. Also no 'spurious retransmissions' are shown in WireShark.

[jchristn]

Got it. Well, let's hope that fixes the issue for you! I was tempted to leave TCP keepalives out of all of my TCP libraries since it's really like dark voodoo magic that happens under the hood, and no controls/notifications are provided when the kernel takes action. Would you mind keeping me updated on how it looks after some time? Cheers, Joel

[w123u567]

Also the 'spurious retransmissions' may be of concern - it indicates that Wireshark has already seen the ACK, but perhaps the ACK was not received by the sender.

Are your client and server on the same LAN segment, i.e. there's no router in between them (other than perhaps a WiFi router)?

https://www.chappell-university.com/post/spurious-retransmissions-a-concern

If I use the client in the same Network everything was fine, only if I connect from outside of my private network (port forwarding is set correctly)

[w123u567]

Got it. Well, let's hope that fixes the issue for you! I was tempted to leave TCP keepalives out of all of my TCP libraries since it's really like dark voodoo magic that happens under the hood, and no controls/notifications are provided when the kernel takes action. Would you mind keeping me updated on how it looks after some time? Cheers, Joel

Yes, I hope it will work now. I will do some tests and let you know if the problem is fixed. Thank you very much for the support :) 👍

[w123u567]

No more unwanted disconnects since I set _server.Keepalive.EnableTcpKeepAlives = false;. I will close this issue and hope for the best :)