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kotlinlang

Hi all, is it possible to detect if a websocket session was closed by the client? I'm getting some weird errors when a client closes the connection by leaving the page.

It's not related to ktor actually, it's due a channel that I create. In order to avoid having Websocket interfaces (such as Frame.Text) on my business classes I connected both using a channel

```  webSocket("/arenas") {
                val channel = Channel&lt;Status&gt;()

                frameUpdater.subscribe(channel)
                for(status in channel){
                    outgoing.send(Frame.Text("timestamp: $status"))
                }
            }```

it works fine when connections are alive, the `frameUpdater` has a suspended function that keeps producing data to the channel

And what happens when the use closes the tab?

but when the connection is closed, I get an error that the `channel` is no longer opened, and it's not like I'm getting the error on the producer side, it's actually at the `for` loop

that makes sense, probably it happens on the `outgoing.send` method

I guess that’s the expected behaviour, right?

I guess if the error was in the send, that's what trigged my question. Error is on the receive side, which is odd. I should have better treatment for the producing side checking if the channel is closed and if it is remove it from the produce operation

I guess you should wrap the function after subscribe in a try..catch + finally, ignore expected errors for connection close, and unsubscribe on the finally block
?

the producer is not bound to that websocket as far as I understand from that snippet

as I understand you have a producer outside not bound to any websocket, and then you are doing a fanout to each websocket with the produced information

so it really seems that because the outgoing channel is closed the exception was being bubbled up, a bit weird where the stacktrace reports it though

Thanks for the help :slightly_smiling_face:

didn’t checked the stacktrace, though without asynchronous stacktraces enabled things are usually a bit weird, yes :slightly_smiling_face: so maybe it had sense somehow, but was far from obvious