hi, ``` suspend fun ServerSocket.listening() = sus...

# coroutines

[halim]

hi,

suspend fun ServerSocket.listening() = suspendCancellableCoroutine<Socket>{ 
    it.invokeOnClancellation { println("coroutine is cancelling...."); close() }
    it.resueWith(Result.success(accpet())
}

fun main() = runBlocking() {
     withTimeout(3000) {
           val socket = ServerSocket(4000).run { listening() }
     }
}

i expected to cancel after 3 sec but not think happen, server still listening and wait for client to connect
why suspendCancellableCoroutine not cancelled ?? any idea

[tseisel]

IO in Java, such as Sockets and InputStreams are blocking by nature. Wrapping blocking code with coroutines does not make it magically suspending ; you have to do the blocking stuff on another thread (for example, calling accept in a withContext(<http://Dispatchers.IO|Dispatchers.IO>) block) to prevent from blocking the main thread

[halim]

thanks, even if use withContext(....) and try to cancel does not work !!! mots IO in java is blocking so in witch suspendCancellableCoroutne is usefull ??

[gildor]

suspendCancellableCoroutine is useful of course, but not sure that it will work without wrapping to own coroutineScope where blocking and cancellation are dispatched on different threads

[gildor]

Just wrapping to withContext will not help, you again just wrapping one blocked thread that cannot dispatch cancellation

[halim]

thanks