WebSocket support

Have you ever thought about adding WebSocket support?

I am looking for a way to push XML messages to clients to enable multi-client xml-applications and WebSockets would be an ideal fit. I added a %rest:WEBSOCKET annotation to test the concept and got it to work, so I was wondering if something like this was ever on the roadmap for BaseX/RESTXQ?

Thanks! Mike

[jfinckh]

The first implementation of websockets can be found in the masterbranch now.

Import in XQuery:

import module namespace ws = "http://basex.org/modules/Websocket";

Overview of the new Annotations:

• ws:connect(path) -> Called when a Websocket connects
• ws:message(path,message) -> Called when a Message arrives
• ws:close(path) -> Called when a Websocket closes
• ws:error:(path,message) -> Called when a Websocket throws an error
• ws:param(name,variable[,default]) -> For getting additional Parameters

Possible ws:param’s:

• Http-Version -> f.e.: %ws:param("Http-Version", "{$version}")
• Origin
• Protocol-Version
• QueryString
• IsSecure
• RequestURI
• Host
• Sec-WebSocket-Version
• offset -> just for binary-Messages
• len -> just for binary-Messages

Overview of new Functions

• ws:emit(message) -> Emits a Message to all Connected Clients
• ws:broadcast(message) -> Broadcasts a Message to all Connected Clients except the Caller
• ws:send(message,id) -> Sends a Message to the Client with the id id
• ws:id() -> Returns the Id of the Caller
• ws:ids() -> Returns the IDs of all connected Clients
• ws:get(key) -> Returns a WebsocketAttribute of the calling Client
• ws:get(id,key) -> Returns a WebsocketAttribute of the Client with the id id
• ws:set(key,value) -> Sets a WebsocketAttribute of the calling Client
• ws:set(id, key, value) -> Sets a WebsocketAttribute of the Client with the id id
• ws:delete(key) -> Deletes a WebsocketAttribute of the calling Client
• ws:delete(id, key) -> Deletes a WebsocketAttribute of the Client with the id id
• ws:path() -> Returns the Path of the calling Client
• ws:path(id) -> Returns the Path of the Client with the id id

The Path is always the Path the Client connects to.

A quick-and-dirty-example for the most of the new Annotations/Functions can be found here: https://github.com/jfinckh/chat/tree/master

We would be pleased about feedback and further extensions.

[usq]

Hi, sorry for the late reply, I was swamped with work the last days.

Thanks for the mailing list link!

I just added https://github.com/TooTallNate/Java-WebSocket, added the %rest:WEBSOCKET annotation and send the serialized XML via the WebSocket to all connected clients when creating the RestXqResponse. But this was just for a prototype and is far from production code!

The websocket support is actually part of my master thesis on multi-client XML applications. I need to notify a group of connected clients about changes to the database (e.g. for an XML chat application, or multi-client word processing like Google Docs)

At the moment, I’m trying to figure out an API/annotation-parameter to specify that WebSocket messages should only be sent to either all clients, a subgroup or just one. An example would be a chat server, which allows users to join specific chat rooms. As soon as a message is posted and stored in the database, only the clients inside the room should receive a WebSocket message containing the new database state.

As soon as I got that, I’ll post a clean/non-hacky pull request (adding the WebSocket like mentioned on the mailing list).