Target specific socket connections?

[peteruithoven]

Is there any way to target specific socket connections, from an instance that doesn't have the connection to that socket connection?
I'm afraid this requires similar functionality as rooms, which also isn't implemented yet.

[objectiveSee]

If you need to emit events to socket.io instances from a non-socket.io process, you should use socket.io-emitter.

[peteruithoven]

Thanks I'll have a look at that, maybe there is a workaround there.
But I'm actually in the situation where I use a clustered socket.io server. Now I would like to forward a message from one client (that's for example on instance A) to a specific other client (that's for example on instance B). So all instances are socket.io servers.

[shantanuthatte]

Use rooms, and send the message to the room with the client you desire.
Every client gets its own room with a unique id. So, sending it just to the
room with the id would work.

Regards,
Shantanu Thatte
On Oct 1, 2014 4:24 PM, "Peter Uithoven" notifications@github.com wrote:

Thanks I'll have a look at that, maybe there is a workaround there.
But I'm actually in the situation where I use a clustered socket.io
server. Now I would like to forward a message from one client (that's for
example on instance A) to a specific other client (that's for example on
instance B). So all instances are socket.io servers.

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#30 (comment)
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[peteruithoven]

I'll try.
I'm sorry I forgot to mention that I would like to use acknowledgment callbacks. I tried putting the target client into a room with a custom name (so I don't have to store the socket.io id in a database), but then it becomes a broadcast (to possible multiple clients) and then I can't specify a acknowledgment callback. So I tried retrieving the clients from a room, so I could target them specifically, but retrieving the clients from rooms isn't possible yet (#13).

[peteruithoven]

I just want to confirm that talking to a client of another socket.io server can be done by using their socket.io id as room name. It also works when you put this target client in a custom room with a fixed name and talk to that room from another socket.io server instance.
This means that socket.io-redis does support rooms, it just can't list the clients in rooms. It probably can't list the rooms that exist in other servers either.

But sadly, emitting into a room is considered broadcasting, probably because there can be multiple clients in a room, so you can't use callbacks. You'll get the following error when trying:

Callbacks are not supported when broadcasting

[peteruithoven]

So I see two possible solutions:

• Find a way to create a fake socket (so I can use existing callback code)
• Broadcast to a room and build my own callback system, see: Need ability to arbitrarily emit with callback to a socket client. socket.io#1656 (comment)

[peteruithoven]

I created a redis pub/sub wrapper with a callback system. This allows me to, from one instance, execute a emit on another instance and retrieve the response using a callback.
https://www.npmjs.org/package/redis-pubsubber