Websocket support

[JavaJens]

As #127 is a little overloaded and goes beyond the technical, I thought to open up this issue to gather implementation details and coordinate efforts for this.

Support for WebSockets is already present on the server, so the idea is to use WebSockets on Android as well (for now instead of a possible more suited protocol like MQTT)

@geileszeuch mentioned a guide on how to use websockets in native apps: http://www.elabs.se/blog/66-using-websockets-in-native-ios-and-android-apps

However I don't think this would be a good guide as it doesn't talk about Wake/Sleep and connection loss.
This article list several issues one has to deal with in a mobile enviroment: http://dalelane.co.uk/blog/?p=1599
I believe the approach mentioned here http://stackoverflow.com/a/16602970 to be reasonable, if I find the time I will give it a try.

I guess for developing this one has to run an own server, as WS is disabled per default.

So please, if you have a question, concern or are already working on this: comment!

Is there any technical reason to use web technology ? why not any XMPP like ?

[JavaJens]

There is already support in the Server :)

As you said, a mobil environment is likely to break connections and thus we will be force to reimplement what already exists in session protocol like XMPP or SIP that is registration, session management, etc.

I think it would be easier to develop something on top of a session protocol even though it will require some slight modification on the server side.

[JavaJens]

Do you have anything particular in mind? I haven't checked the code, but
maybe the GCM server part is using XMPP already which could be reused?
I know @v-0-d mentioned MQTT in the other thread, which sounds pretty good
as well.

Nevertheless, I think the current server can handle session mobility to
some extend, but I haven't looked very thoroughly.
From what I see the client simply has to connect (and reconnect if needed)
to the server and listen to incoming messages which are queued until
delivered. And as a client as a clear identification number the mapping to
a WebSocket connection shouldn't be such a big deal.

[JavaJens]

I've created a local branch with very rudimentary support, more a PoC: https://github.com/JavaJens/TextSecure/tree/feature-1000
Maybe @thors you can take this as a starting point?
@TheBlueMatt is working on the desktop client afaik. Maybe he can provide some insight to the registration for WebSocket devices?

[geileszeuch]

He recently open sourced bis early version of the textsecure browser extension. Hopefully this will provide some insight: https://github.com/TheBlueMatt/textsecure-chrome

[JavaJens]

Yes, I looked into that. right now multiple devices can be registered on one number.

For the Android version i've got to make little changes therefore.

Right now the device connects and all seems well, I only have to test sending/receiving messages which doesn't work right now.

Probably because I only have one device and try to work with the emulator and a modified server version.

If you want you can checkout my feature branch and test yourself :)

cheers

[Manuel-Kehl]

Thank you for your efforts! I will checkout your branch as soon as my current exams are over and maybe even contribute something.

I hope that we will soon be able to (optionally) use TextSecure without GCM (and PlayStore in general!).

[SecUpwN]

@JavaJens, thank you for opening up this issue, I can't wait for this to be implemented! ;-)

[JavaJens]

Feel free to test by branch and contribute. Sadly I'm pretty busy right
now, but rudimentary support exists :)

[SecUpwN]

@JavaJens, is there a compiled WIP-version somewhere or do I have to compile it by myself?