Server received TCP FIN before WebSocket close frame

[toini]

I'm debugging an issue with evcc and noticed that when v0.14.0 of this client reconnects it appears to close the connection by calling conn.Close() without first sending a close frame. I think according to RFC6455 a close frame should be sent.

This, in combination with a recent change on our server makes it unable to decrement a client connection counter which makes the server block the connections from the client which currently makes the client reconnect again after 5 seconds leading to issues with unusually high traffic.

I'll adjust the server to handle the situation more gracefully, but I think it would also be a good idea to make this client send a close frame?

[hgiasac]

AFAIK, it is handled by the WebSocket client itself. This is out of the subscription client's scope.

[toini]

Yes, websocket client does indeed send the close frame but it appears we get TCP FIN already before that. Maybe you can see it in the screenshot. Could it be that something cuts the connection already before close() is called?

[hgiasac]

This issue may be related. Let's see if we can work around that. Otherwise, you can implement a custom WebSocket handler using the Gorilla client that the issue author mentioned.
coder/websocket#507