Allow access to OkHttp's WebSocket type

[JakeWharton]

interface Service {
  @GET("/chat/{id}")
  Call<WebSocket> chat(
      @Path("id") String id);
}

[swankjesse]

Whoa.

[JakeWharton]

There's problems here:

WebSocket is solely a writing type. Messages that are read come in as callbacks to the WebSocketListener which is also what has the open/failure callbacks. Additionally, we are re-using the failure callback for both setup failure and then protocol or transport failure down the line.

A potential solution would be to split the listener into two callback classes: one for the connection and one for messages. This could be done either here as a set of wrappers, or in OkHttp. You may remember that my initial API for WebSocket was done in this way before you commented that we could consolidate them into one.

However, the split is not entirely a solution because we have a threading problems. When we get the WebSocket instance in onOpen we are on the reader thread. Once that method returns, it sits on the loop reading messages from the wire. If the call adapter choses to move threads before handing the WebSocket to the caller, there's a timing issue where messages might be dropped because a listener has not been set.

One potential solution would be to do the callback split, change onOpen to onConnected, and add a method like start(WebSocketListener) to WebSocket. This would just be a CountDownLatch that holds the reader thread up for a period of time (like the connect timeout that we already have on the OkHttpClient) in case threads need to be moved.

I don't have other solutions in mind yet so I'm open to those and thoughts on what I proposed above.

[swankjesse]

We'll want Retrofit's web socket to make onMessage take a <T>, and similarly for sendMessage.

I'm guessing Retrofit will encapsulate OkHttp's WebSocket and layer its own abstraction on top, to handle type adapters and threading. This is symmetric with Call, right?

[JakeWharton]

Making it typed is very interesting. And that will of course require an abstraction. I'll experiment with it.

[JakeWharton]

APIs to look at for inspiration/samples:

• Slack: https://api.slack.com/rtm
• IRC Cloud: https://github.com/irccloud/irccloud-tools/wiki/API-Stream-Message-Reference
• Chrome DevTools: https://developer.chrome.com/devtools/docs/debugger-protocol
• Trello: Not documented online beyond the WebSocket connect endpoint, but you can use Chrome DevTools to inspect.

[JakeWharton]

Thinking about this more, I think it requires a WebSocketCall type in Retrofit which is parameterized on incoming type I and outgoing type O. Unfortunately this presents a problem for call adapters since they won't work with this type.

[JakeWharton]

Here's the untested prototype so far: https://github.com/square/retrofit/compare/jw/websocket

[trustratch]

I would like to see this happen, how can i help you guys

[frxncisjoseph]

Still waiting... :-(

[frxncisjoseph]

I'd at-least like some sort of update please? Is this going ahead or not?

[jjhesk]

how about now? any updates? its almost 2017

[JakeWharton]

Updates will be put as comments in this issue. No new comments means no new updates.

On Tue, Dec 13, 2016, 2:00 PM 世外桃源 notifications@github.com wrote:

how about now? any updates? its almost 2017

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[taejungkim]

I did not find anything about Web Sockets in Retrofit version 2.2. (https://github.com/square/retrofit/blob/parent-2.2.0/CHANGELOG.md) When will you add a web socket to Retrofit?

[JakeWharton]

There is no timeframe

On Sat, Mar 11, 2017, 10:53 PM taejungkim notifications@github.com wrote:

I did not find anything about Web Sockets in Retrofit version 2.2. When will you add a web socket to Retrofit?

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[taejungkim]

I will use Okhttp version 3.5 websocket. However, I hope Retrofit will support web sockets.

[MateuszNaKodach]

When we should expect web sockets in retrofit ;) ?

[forresthopkinsa]

@nowakprojects For now, I think it's safe to assume that

There is no timeframe

[EnnaKenT]

Is there any news?

[frxncisjoseph]

@EnnaKenT Don't sell yourself dreams.

[Albert221]

- knock knock - who's there? - developers waiting for Websockets in Retrofit - uhm, sorry, nobody's home now

[JakeWharton]

I'm available to hire to do this work, but if you want it for free then it's going to be on my schedule. Enjoy the rest of the free code in the mean time!

On Sat, Apr 7, 2018, 8:43 AM Albert notifications@github.com wrote:

• knock knock
• who's there?
• developers waiting for Websockets in Retrofit
• uhm, sorry, nobody's home now

— You are receiving this because you authored the thread. Reply to this email directly, view it on GitHub https://github.com/square/retrofit/issues/924#issuecomment-379466703, or mute the thread https://github.com/notifications/unsubscribe-auth/AAEEEVx_Sojk3eIBYdC2ZLTwsatkyDTEks5tmLRkgaJpZM4FNFSf .

[swankjesse]

Umm yes I’ll pay when can you start.

[forresthopkinsa]

All in support of locking this thread until it becomes relevant?

[JakeWharton]

I don't think that's necessary. With any luck we'll be able to knock this out in the next few months.

On Mon, Apr 9, 2018, 11:08 AM Forrest Hopkins notifications@github.com wrote:

All in support of locking this thread until it becomes relevant?

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[mhdtouban]

For those still waiting for WebSocket support.. tinder came up with Scarlet a Retrofit for WebSockets. https://github.com/Tinder/Scarlet

[forresthopkinsa]

@mhdtouban and it's in Kotlin, too! Gorgeous.