I have a super simple embedded server But running it on an i

Question

I have a super simple embedded server But running it on an iOS simulator I frequently get `PosixException AddressAlreadyInUseException EADDRINUSE 48 Address already in use` Does anyone know if there s a way of registering an uncaught exception handler to the Ktor server so I can handle this gracefully Or a proper fix would be welcome I ve tried wrapping the whole thing in a coroutine scope launch block with a coroutine exception handler but that doesn t work ```embeddedServer CIO port = 8080 routing get call respondText Hello world start wait = true ```

ephemient · Answer

if you use `port = 0` it should automatically choose a free port after it is started you can find what port it ended up on through ` resolvedConnectors `

Sam · Answer

Ah that should allow me to come up with a work around Thanks Don t suppose you know how to catch that exception though

ephemient · Answer

does a normal `try` `catch` around ` start ` not work I don t know if there s any iOS specific oddities there

Sam · Answer

Sadly not There s something strange happening once I ve patched this pretty critical issue I ll come up with a minimal reproducible example What seems to happen is that I can catch and log the exception but for some reason it also crashes the app So I think what s happening is that it s somehow being thrown from multiple places

ephemient · Answer

the other solution would typically be to use the `SO REUSEADDR` socket option see <https stackoverflow com a 2270357> for explanation but it doesn t look like `embeddedServer` has any way to customize how the server socket is bound disappointed

Sam · Answer

Yeah I came to the same conclusion do you know if it s possible to reproduce the `embeddedServer` behaviour at a lower level to access this api From what I can see it only seems to be exposed to JVM If you don t know off the top of your head that s cool just wondering

Sam · Answer

Also < ephemient> you ve saved my skin with that `port=0` trick thank you so much heart

ephemient · Answer

I suppose you could re implement most of the `embeddedServer` behavior I don t think it s using anything internal but it looks like a pain

ephemient · Answer

luckily the `port=0` trick is a fairly common use of the socket API it s not just a ktor thing

Sam · Answer

Did not know that noted Yeah pain was my conclusion too I think I might have to try thanks for your help

ephemient · Answer

FYI this is now possible in KTOR 2 3 0 ```embeddedServer CIO port = 8080 configure = reuseAddress = true ```

Sam · Answer

I ve been following the PR too Thanks for the heads up tho