I am currently working on an Android Application in which XMPP is used for communication between users. Now I need to add a function for importing friends from Facebook or the phone contact-list.
Does anyone know how this might be accomplished (that is, if all contacts are available, how to find out which ones are using my application and what their JID is)?
If everyone registers their account with the same email they use on Facebook and you could add friends through their email rather than their JID I can see how it could be done, but it seems like bot a stupid assumption to make, and as far as I know, you can’t add a user with only their email.
There is no standard way to deduce an XMPP address from an email address.
Some services allow the same address to be used for email and XMPP – such as gmail.com. One way to detect whether a given domain has XMPP support is to check for the presence of SRV records, a hackier way is to check whether it is listening on port 5222/5269.
Still, even given an email address and knowing the email host also serves XMPP does not guarantee that user1@example.com is the same user for email and XMPP. Don’t ask me why it ever wouldn’t be, but you can’t make the assumption.
You say that you only need to check for other users of your application. You could store your own database mapping email addresses of accounts to JIDs. I agree with you that this isn’t ideal – but that is exactly how most services that do this work. Including Facebook, except they have a lot more data than just your email address…).