Question

I want to use XMPP to push data to my client which would translate to a notification for the user, and plan on using their google-id for login to my application. The way I understand XMPP is that its a simple message that goes directly to the adress, but I want the client to get it as instructions and turn it into gamestate information.

It would be very frustrating for a user to get a bunch of command tuples or hex garbage in their google chat! Am I misunderstanding the way this all works?

Answer 1

JIDs (Jabber/XMPP IDs and therefore Google Talk IDs) have several forms.

First is a “bare JID”, e.g.: [e-mail]
Secondly is a “full JID”, e.g.: [e-mail]/xyz123, where xyz123 is called the resource.

One user can be logged into their XMPP account from multiple clients simultaneously, so long as each client uses a unique resource. With Google Talk, usually the server allocates the resource.

When you talk to someone on XMPP normally you address messages using their bare JID — you don’t care about which client the message gets delivered to; that person’s server directs it to the appropriate client(s) based on their availability etc.

But you can also address a message directly to a full JID. This is what you want to do, so that only [e-mail]/my-game-some-unique-ID receives your game-specific messages.

Whether the Google App Engine API gives you this flexibility, I have no idea 🙂

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An alternative — again, if GAE allows this — is to send a different message type.
XMPP is eXtensible, meaning that you don’t have to send a plain old <message/> stanza to the end user; you can stick a specialised payload inside there like a <game/> child stanza and, because regular IM clients don’t know how to parse your <game/> stanzas, they show nothing to the user. Only your game client will parse and understand this info.