Django and websockets: Channels vs Socket.io vs other

This can be done using a WCF CallBack contract.

If the client can make a connection to the server, the server can use a WCF service with a callback construction. This describes that the server expects the client to implement a service as well (the callback service), as part of the service contract.

This beaks down as follows:

1. The server hosts a WCF service.

2. The service contract has a CallBackContract attribute:

   [ServiceContract(CallbackContract = typeof(IMyServiceCallback))]

3. Clients that want to use this service, must implement the desired callback contract (service) to be able to communicate with the server.

4. When a client connect with the server side service, the reverse / callback connection will be made over the same connection.

Using callbacks is done over the same connection (that has already been opened). This requires a two-way communication channel (for example http).

See http://adamprescott.net/2012/08/15/a-simple-wcf-service-callback-example/ for an example how to implement this.

Although you asked this a year ago, I have a solution! One you may have use for if you are still using socket.io

Hey I came across this precise issue while creating a haiku sharing application (you can check it out at http://haiku.run )

You can see my source code hosted on github at http://github.com/sova/haiku.run

Check out the code for index.js https://github.com/sova/haiku.run/blob/master/src/index.js#L95

on Line 95 there is the following code:

clients[clients.indexOf(socket)].emit('load_haiku_from_cache', a_latest_haiku);

Basically, when a new user connects, I want to load the cache of haiku that are stored in RAM on the node app in a variable called haiku_cache or something like that. There's 7 of them in the cache, and they get emitted when a user freshly connects.

However, it's different because now if a new user, say user 2 connects, then user 1 would (normally) get a double update of the cache in their socket-spurned-feed of stuff.

So, the above code effectively emits information along one particular socket.

In conclusion, I recommend you keep track of all the sockets that you wish to receive a particular set of informations, and then use the above-like line to send to specific sockets. You can emit across the wire / over the socket to one specific connected client, which is really nice, using the above line.

Hope that helps anybody looking around for a good solution to "how to emit to a subset of connected peers" since the group/room socket.io stuff is kinda messy imho.