Using channels without js simply means you need an implementation of phoenix.js for your mobile app. Phoenix channels are not just raw websockets, but a communication protocol on top of many transports – websockets being one of them. Therefore your app needs to be able to communicate using that protocol. In detail this means being able to negotiate a serialization protocol for messages. Being able to serialize/deserialize messages according to said protocol, understanding a handful of channel specific messages as well as dealing with all the app specific messages. Then you’ll need facilities for handling channel joins/connection, dealing with replys and such. And if you need it (and it sounds like you do) you also need to deal with presence messages and the diffing mechanism.

As for tracking connectivity. Websocket connections will terminate once disconnected, but especially for flaky network this can be unrelyable for detecting disconnects. Therefore there are heartbeats as part of phoenix channels. I’m not sure currently if there’re initiated by the client or by the server though, but it’s likely the client.

No, if there is no web UI then you do not need to care.

Write tests. There are also CLI tools for connecting to WS.

You need not only to connect to WS, but you also need to talk proper protocol, in this case Phoenix protocol defined in Phoenix.Socket.V2.JSONSerializer.

For testing channels you can use Phoenix.ChannelTest helpers.

if you search for heartbeat in that repo it’s there Repository search results · GitHub
I assume it’s handled automatically..

I haven’t done anything in swift but there is an example project there https://github.com/davidstump/SwiftPhoenixClient/tree/master/Example/ChatExample with specific code here:

https://github.com/davidstump/SwiftPhoenixClient/blob/master/Example/ChatExample/ViewController.swift