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Ktor works great so far, for HTTP requests at leas...
# ktor
s
Ktor works great so far, for HTTP requests at least. But I'm having an issue with the websockets in creating a connection to the Discord API servers. Using the same headers and parameters for both Ktor's websocket library and Http4k's nv-websockets, only Http4k manages to create the connection, while Ktor sends an invalid request (403).
d
If you manage to gather more information (the valid request / and the invalid one) that would help a lot. You can write an issue here: https://github.com/ktorio/ktor/issues
s
@Deactivated User Will do. I have a few hours to kill anyway
🙏 1
Still looking, haven't found anything obvious that would cause a 403.
d
Can’t you dump a request that works, and a request that doesn’t?
s
The request is as default as it gets. The only parameter I give to Http4k is the URI 
<ws://gateway.discord.gg/>
, and the same to Ktor. I can't manually create a websocket request to that endpoint using Ktor, since the 
Upgrade
header is locked.
I'm using the debugger to try to find differences in what's sent to the endpoint.
d
Yeah, I was thinking for example in wireshark to dump one working and other not working and see differences. Especially it if it is ws and not wss shouldn’t require anything special.
s
Didn't even know about wireshark, I'll install it and give it a shot. You've just made this 10x easier 😄
🙂 1
It's wss. I had the program request a valid endpoint from Discord before attempting to connect, and upon further inspection, attempting to connect with 
ws
throws a 404, even with Http4k.
d
I see. I guess it would be possible to intercept Java calls to the stream to get the data without encryption, but I have not investigated that case so I don’t know the details
s
Ktor connects to the endpoint when using wss, but I need to be able to keep a reference to the WebSocketSession, and there's no 
webSocketSession
complement for the 
wss
function. Any ideas?
d
in the worst case you can compile the library used from source modifying it to dump the write stuff to a file too
uhm
if that’s the case, maybe you can create a PR or a issue about that missing method. You can also look at the sourcecode and create the extension method in your code in the meantime: https://github.com/ktorio/ktor/blob/master/ktor-client/ktor-client-features/ktor-client-websocket/src/io/ktor/client/features/websocket/builders.kt
another possible option is to create a WSS reverse proxy and dump stuff there
you can even use ktor for that
s
The option I've gone for is to store the outgoing SendChannel and use that, while using the 
wss
function to create the socket.
👌 1
I can still create an issue for the lack of a 
secureWebSocketSession
though, if you'd like
d
yeah if you think it is missing, makes sense to add it
s
Run into another issue. It doesn't seem like anything I put into the outgoing channel is actually sent
d
how are you using websockets?
as far as I understand you are using the ktor websocket client to connect to a wss api from discord, right?
so you are not using channels directly, right?
s
Yes
Well
Discord's connection process is... let's say "involved".
d
do you need to send other things other than normal frames?
s
Once the secure websocket is opened, a payload is sent to the client that contains information about the session. The client is supposed to then send information about itself, including the operating system and bot token.
d
in the same http request?
once the Ws upgrade is done, it just should let you to send frames
https://en.wikipedia.org/wiki/WebSocket#Protocol_handshake the request + the server responds with an upgrade then everything should be frames
s
Copy code
client.wss(host = "<http://gateway.discord.gg|gateway.discord.gg>") {
        outgoingChannel = outgoing
}
then, later on, after the session info is received from the socket:
Copy code
outgoingChannel?.send(Frame.Text(text))
outgoingChannel
isn't null at this point either, and no exception is thrown. It just does nothing, as far as I can tell.
d
but I don’t know why are you trying to change the outgoingChannel
for interception/debugging?
s
I'm not. 
outgoingChannel
is a class-level variable that I'm using in leiu of storing the 
WebSocketSession
itself.
d
uhm
s
So instead of storing the session, I store the 
outgoing
channel, and use that to send frames.
d
aha
and the frames you are trying to send with those methods
are not written to the socket?
s
Yep. No exceptions are thrown, but nothing is written to the socket as far as I can tell.
d
that might be a bug, I can’t tell without all the context. Which version of ktor are you using?
s
1.0.0-alpha-1. I can commit this and push it to Gitlab if you'd like to take a look.
d
if it is not too large I think I can have a look
by chance have you tried with an older ktor version just in case? Or created this code after 1.0.0-alpha-1?
(Just to discard regressions)
s
I can try it with an older version, sure.
d
Yeah, that would help if it is possibl
s
Happens with 
1.0.0-alpha-2
, 
0.9.6-alpha-1-rc13
, and 
0.9.5-rc13
.
d
aha
well try to upload that sample and I will have a look as soon as I have some time. Also I can try to create a snippet for a WS reverse proxy using ktor so you can intercept the communication and debug both directions
s
Sure. I'll actually try and rewrite it as just a single file, to make it easier to read.
🙏 1
👍 1
I'll need to give you a token to use for authentication, just promise you'll get rid of it once you're done 🙂
d
Im not at the computer right now. I will look at it in a few hours. First i will try to read it without executing it to see if i find something obvious. If not we can try the token. I willalso try to create a ws reverse proxy snippet to debug it
s
https://gitlab.com/serebit/ktor-error-demo The working Http4k version is on the 
master
branch, the not-working ktor version is on the 
ktor
branch.
d
Being private I guess you missed the assignment when simplifying the code
s
Yep, that's what happened. Fixed it.
d
Sorry for the delay. Except of that can’t find anything else strange. Also I have created a sample showing how to create a websocket reverse proxy so you can intercept messages and dump stuff and see if data is being sent: https://github.com/ktorio/ktor-samples/blob/master/other/reverse-proxy-ws/src/ReverseProxyWsApplication.kt#L61
s
Thanks, I’ll give that a try once I get home.
👍 1
So as someone who hasn't touched the server side of ktor, how does this reverse proxy work?
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