search

NanoHttpd / nanohttpd

Tiny, easily embeddable HTTP server in Java.
http://nanohttpd.org
BSD 3-Clause "New" or "Revised" License
6.92k stars 1.69k forks source link

If a close frame fails to send, set the state back to OPEN #504

Open NoahAndrews opened 6 years ago

NoahAndrews commented 6 years ago

Note: This is all based on reading the code for the latest 2.x release, not observation. I could be wrong. I did a quick check of the master branch, and it looks like it works the same way.

Right now, if close() is called on a WebSocket instance, and the close frame fails to send, then an IOException is thrown, and the WebSocket is left in the CLOSING state. If you were to then call close() again, it would finish closing down the socket, without even trying to re-send.

It seems like the correct behavior in this instance would be to catch the IOException, attempt to resend the close frame, and then immediately call doClose().

Maybe my specific idea isn't the best, but I think the code as it exists needs a little reworking.

NoahAndrews commented 6 years ago

Actually, a better solution would be to throw the IOException after putting the WebSocket back in its previous state (a forceClose parameter could be added to override this behavior and finish shutting down the websocket)

LordFokas commented 6 years ago

Actually, the best approach would be to understand why the server would fail to send a close frame and only then think of the correct way of dealing with each scenario.

Tell me, would you be interested in helping rewrite the entire library from the ground up? Patching on top of patches is kinda not cutting it anymore, especially if you take into account how half assed the initial implementations were...

NoahAndrews commented 6 years ago

I'm afraid that's not likely something I'm going to be able to help you with.

LordFokas commented 6 years ago

Well if things do go that way, I intend to do most of the hard work anyways, but having people like you pointing out inconsistencies does help a lot.

Either way, thank you for your contributions so far.

Back to business, since you've been looking into it, how and why do you think it fails to send close frames?

NoahAndrews commented 6 years ago

You're welcome, I hope I'll end up being of further help in the future (I've already got an actual fix for #328 that I need to submit). I'll try to keep track of the code being submitted here going forward.

I've never actually seen it fail to send a close frame. I was just implementing some code that would close all of the open sockets, and of course I had to handle the IOException. Naturally, I went back to look at the code that would throw that exception, and I noticed that if it did get thrown for whatever reason, you'd end up in an incorrect state. I imagine that you could trigger this by disconnecting from the network at just the right split second. So it's not about an underlying issue that needs fixing, just about keeping things sane if an error were to happen.