Hi there,
I wonder if it’s possible to add Discord Rich Presence via the old discord-rpc API to a snap? No matter if I run Discord itself from within a snap or the traditional .deb package from their website, I can’t get the discord integration working in a snap.
I assume just building and adding discord-rpc itself to the app is not enough due to the confined nature of a snap package?
Looking at the docs linked from that site, the IPC involves creating a websocket connection to 127.0.0.1 with one of a number of well known ports:
https://discord.com/developers/docs/topics/rpc#connecting
A snapped client should be able to access that fine if it has the network plug connected (which should auto-connect). As a TCP socket, the snap sandbox shouldn’t be a problem.
You should be able to see if the Discord app is listening by running netstat -lt, and look for something listening on localhost on a port in the range 6463-6472.
The content interface would not currently help, since it won’t handle per-user mounts like this.
Thanks for the feedback! Unfortunately, I don’t see a port exposed by discord-rpc, so connecting network won’t be enough - it uses the discord-ipc-N socket instead.
I think the last resort is to do something like shown in https://github.com/flathub/com.discordapp.Discord/wiki/Rich-Precense-(discord-rpc), but I don’t know if that just refers to Discord distributed as FlatPak itself or FlatPaks connecting to Discord instead.
a little side note …
if such a sentence contains the words ‘connect’ and ‘socket’, you always want network-bind (which auto-connects as well) 
If you’re an application trying to connect to the websocket server run by the Discord app, you shouldn’t need network-bind though. You’d only be establishing outbound connections.
Looks like that indeed it must be ‘something else’ regarding the discord-ipc-X socket file - Discord doesn’t open a local port, so I think the whole network- interfaces are not necessary here (I’m connecting them anyways due to different reasons).
I’ll see if I can do some symlinking magic, maybe the snaps are looking at a different location for the websocket due to the modified $XDG_RUNTIME_DIR.
I missed the text at the top of the page:
For now, RPC is in a private beta. We are not currently accepting any new developers into the program at this time.
So I guess the TCP/websockets based access is not generally available right now, but will be in future.
As far as workarounds go, a symlink probably won’t help since the access will be blocked by AppArmor. You might have luck bind mounting the socket: create an empty file with the right name in the snap’s private XDG_RUNTIME_DIR, then use mount --bind src target to mount the real socket file over the top of the empty file.
Unfortunately, this is not going to happen - this Discord RPC API is deprecated and got replaced with their (proprietary) Discord SDK, which is not GPL-complient and thus can’t be used in the application I’m snapping.
Thanks, I’ll give this a try and check if I can wrap the bind-mount in a launcher script.
No luck so far - the bind-mounts would require permissions the usual user won’t have, so I can’t simply wrap this into a launcher script.
Since the attept symlinking it (like shown in the FlatPak example) didn’t work too, I think we have to consider this as impossible - at least for know.
Unless somebody here has another idea of course 
