Instant messaging server. Backend in pure Go (license GPL 3.0), client-side binding in lots of different languages. Also supports gRPC and HTTP(S)+Websockets. Supports persistent storage with a back-end database.
This is not XMPP, but I added the tag so it's easier to find later.
This is also a proof-of-concept web client: https://github.com/tinode/webapp/
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