I'm looking for a simple messaging server which I can run on my server which will be used to register clients when they are online so they can "talk" with each other (kind of WhatsApp service but much more lightweight). The clients will be Android and iOS devices so I need a compliant client side as well.
The best solution I came up with is XMPP server but I'm not sure that this is the best choice and I'm not familiar with other possibilities.
What do you think about XMPP: is that the right solution or are there any other options?
XMPP is a complete open standard IM protocol with a lot of features implemented besides messaging and presence (via XEP - extensions).
Other IM protocols are listed in this complete comparison table:
So, IMO XMPP is a good choice to implement Android/iOS apps.