How to disable forcibly closed by the remote host?

[ronjunevaldoz]

Ktor Version and Engine Used (client or server and name) implementation "io.ktor:ktor-network:1.3.2"

Describe the bug Using the raw socket example. My existing client (untouchable) is having a duplication connection which is a known issue on client side. But the server is forcibly closing the client connection. I've added some custom socket options to keep alive but it does not work. The coroutine is cancelling when there is an existing connection

 /**
     * Set TCP_KEEP_ALIVE socket option to enable the Nagle algorithm.
     */
    private fun <T : Configurable<T, *>> T.tcpKeepAlive(): T {
        return configure {
            if (this is SocketOptions.TCPClientSocketOptions) {
                keepAlive = true
            }
        }
    }

To Reproduce Simple echo server example from https://ktor.io/servers/raw-sockets.html

fun main(args: Array<String>) {
    runBlocking {
        val server = aSocket(ActorSelectorManager(Dispatchers.IO)).tcp().bind(InetSocketAddress("127.0.0.1", 2323))
        println("Started echo telnet server at ${server.localAddress}")

        while (true) {
            val socket = server.accept()

            launch {
                println("Socket accepted: ${socket.remoteAddress}")

                val input = socket.openReadChannel()
                val output = socket.openWriteChannel(autoFlush = true)

                try {
                    while (true) {
                        val line = input.readUTF8Line()

                        println("${socket.remoteAddress}: $line")
                        output.write("$line\r\n")
                    }
                } catch (e: Throwable) {
                    e.printStackTrace()
                    socket.close()
                }
            }
        }
    }
}

Expected behavior I could have handle the server, whether I choose to force close or not, when having a duplicate connection

Raw Error

Exception in thread "DefaultDispatcher-worker-6" java.io.IOException: An existing connection was forcibly closed by the remote host
    at sun.nio.ch.SocketDispatcher.read0(Native Method)
    at sun.nio.ch.SocketDispatcher.read(SocketDispatcher.java:43)
    at sun.nio.ch.IOUtil.readIntoNativeBuffer(IOUtil.java:223)
    at sun.nio.ch.IOUtil.read(IOUtil.java:192)
    at sun.nio.ch.SocketChannelImpl.read(SocketChannelImpl.java:380)
    at io.ktor.utils.io.nio.ChannelsKt.read(Channels.kt:135)
    at io.ktor.network.sockets.CIOReaderKt$attachForReadingDirectImpl$1$1$1.invokeSuspend(CIOReader.kt:90)
    at kotlin.coroutines.jvm.internal.BaseContinuationImpl.resumeWith(ContinuationImpl.kt:33)
    at kotlinx.coroutines.DispatchedTaskKt.resume(DispatchedTask.kt:175)
    at kotlinx.coroutines.DispatchedTaskKt.resumeUnconfined(DispatchedTask.kt:137)
    at kotlinx.coroutines.DispatchedTaskKt.dispatch(DispatchedTask.kt:108)
    at kotlinx.coroutines.CancellableContinuationImpl.dispatchResume(CancellableContinuationImpl.kt:306)
    at kotlinx.coroutines.CancellableContinuationImpl.resumeImpl(CancellableContinuationImpl.kt:316)
    at kotlinx.coroutines.CancellableContinuationImpl.resumeWith(CancellableContinuationImpl.kt:248)
    at io.ktor.network.selector.SelectorManagerSupport.handleSelectedKey(SelectorManagerSupport.kt:84)
    at io.ktor.network.selector.SelectorManagerSupport.handleSelectedKeys(SelectorManagerSupport.kt:64)
    at io.ktor.network.selector.ActorSelectorManager.process(ActorSelectorManager.kt:73)
    at io.ktor.network.selector.ActorSelectorManager$process$1.invokeSuspend(ActorSelectorManager.kt)
    at kotlin.coroutines.jvm.internal.BaseContinuationImpl.resumeWith(ContinuationImpl.kt:33)
    at kotlinx.coroutines.DispatchedTask.run(DispatchedTask.kt:56)
    at kotlinx.coroutines.scheduling.CoroutineScheduler.runSafely(CoroutineScheduler.kt:571)
    at kotlinx.coroutines.scheduling.CoroutineScheduler$Worker.executeTask(CoroutineScheduler.kt:738)
    at kotlinx.coroutines.scheduling.CoroutineScheduler$Worker.runWorker(CoroutineScheduler.kt:678)
    at kotlinx.coroutines.scheduling.CoroutineScheduler$Worker.run(CoroutineScheduler.kt:665)

[oleg-larshin]

Please check the following ticket on YouTrack for follow-ups to this issue. GitHub issues will be closed in the coming weeks.

[Stexxe]

@ronjunevaldoz could you please describe the steps to reproduce this problem using your code example?