Hello Teams :smile: I am doing my server with kto...

# ktor

[Nicolas]

Hello Teams 😄

I am doing my server with ktor and I used webSocket to do a chat, I hope my question will not be dumb because I am iOS developer at firt 😄

I have the following code to set up my WebSocket with ktor.
My problem is the following: if I turn off the internet on the mobile side (iOS) after setup a connection with the socket for about 3 minutes, my socket is no longer active, probably because the ping/pong fails on front side from iOS side .

However, the finally block on server side is often called a long time ago, so the webSocket is close after 20 minutes.

How can I prevent this memory leak? and to be sure that after 3minute offline from the client, the webSocket will be remove from my server please.

I Have setup the ping pong like this

fun Application.configureWebSocket(){
    install(WebSockets) {
        pingPeriod = 15.seconds
        timeout = 15.seconds
        maxFrameSize = kotlin.Long.MAX_VALUE
        masking = false

    }
}

routing {
    webSocket("ws") {
        val token = call.request.queryParameters["token"]
        if (token == null) {
            close(CloseReason(CloseReason.Codes.VIOLATED_POLICY, "No Token"))
            return@webSocket
        }

        val decodedJWT = try { JwtFactory.buildverifier().verify(token) }
        catch (e: Exception) {
            close(CloseReason(CloseReason.Codes.VIOLATED_POLICY, "Invalid Token: ${e.message}"))
            return@webSocket
        }

        val userId: UUID = try { UUID.fromString(decodedJWT.getClaim(JwtClaimConstant.claimUserId).asString())  }
        catch (e: Exception) {
            close(CloseReason(CloseReason.Codes.VIOLATED_POLICY, "Invalid Token: ${e.message}"))
            return@webSocket
        }

        val sessionId = decodedJWT.id?.let {
            runCatching { UUID.fromString(it) }.getOrNull()
        } ?: run {
            close(CloseReason(CloseReason.Codes.VIOLATED_POLICY, "Invalid or missing sessionId (jti)"))
            return@webSocket
        }
        <http://logger.info|logger.info>("$userId is connected")

        try {
            println("$userId start")
            incoming.consumeEach {
                when (it) {

                    is Frame.Text -> {
                        val text = it.readText()
                        println("tototot $userId Received: $text")
                    }
                    is Frame.Close -> {
                        println("tototot $userId WebSocket closed by server with reason: ${it.readReason()}")
                    }
                    is Frame.Ping -> {
                        println("tototot $userId ping: $it")
                    }
                    is Frame.Pong -> {
                        println("tototot $userId pong: $it")
                    }  else -> {
                        println("tototot $userId else: $it")
                    }
                }


            }
        } catch (e: Exception) {
            println("$userId error $e")
         } finally {
            println("$userId finally remove")
        }

        println("$userId end")
    }
}

and I found something weird If I open a websocket on my iOS phone, turnoff the internet (and close my phone) I keep logging this on KTOR:

io.ktor.websocket.WebSocket - WebSocket Pinger: received valid pong frame Frame PONG

For me if I close my phone the webscket should try a ping and should not receive a pong and close, For me the goal of ping pong is to avoid all this. I am not sure if I have doing everything good 🙂

I am hosting my server on Render

Thank you in advance for your time

[Aleksei Tirman [JB]]

I've left a comment in https://stackoverflow.com/questions/79668761/websocket-never-closed-on-ktor

[Nicolas]

hello @Aleksei Tirman [JB] thank for your answer, I have the issue only on the server 😢
I have no issue with the client, if I turn off the wifi the websocket connection from the client will close but not the websocket connection from server it will be stay alive 20 minutes left

[Nicolas]

but to answer to your answer it's look like the pong is received on the server

because I have this log

TRACE io.ktor.websocket.WebSocket - WebSocket Pinger: received valid pong frame Frame PONG (fin=true, buffer len = 76)

[Nicolas]

I don't knwo were from the pong because my iPhone was turn off for this test

[Aleksei Tirman [JB]]

Can you please check the timestamps of those messages?

[Nicolas]

I have this message each 15 secondes during 20 minutes

[Aleksei Tirman [JB]]

Even if you turn the network connection off on your client?

[Nicolas]

yes

[Nicolas]

and even my phone close

[Aleksei Tirman [JB]]

Can you please try to reproduce the problem with another client?

[Nicolas]

I have only try with iphone

[Nicolas]

I don't have other client

[Nicolas]

hello 😄

[Nicolas]

but for me the issue don't come from client

[Nicolas]

because the phone it's off

[Aleksei Tirman [JB]]

I don't quite understand what sends the PING frames if the phone's network is off. Can you please check that with a traffic analyzing tool like Wireshark?

[Nicolas]

ktor sever host on Render send a ping to turn off iphone and In the log It say that received a pong

but if you try to connect with an iOS on webSocket (or android phone) and close your phone the websock will close on your side 🙂 ?

I don't know how to use Wireshark 😢