At work, we use our own XMPP/Jabber server for corporate internal instant messaging and contact with permanent customers. Our jabberd2 server provides chat, group chat rooms and file transfers via proxy65. We have become very dependent on it, and cannot do and do not want to work without it anymore.
Every now and then, our internet connection breaks down and we are offline. Panic spreads then because we are unable to determine where to go for lunch, because chatting does not work.
A way to be able to chat even without having our XMPP server available is using link-local, serverless messaging as defined in XEP-174 . It uses zeroconf networking and the jabber protocol for direct client-to-client chat sessions. Some Jabber clients like Pidgin, iChat and Empathy already support that. All others are left out.
Slimber
I personally like and use Psi for chatting, and Psi does not support serverless messaging. Swift, a new XMPP client contains Slimber, a link-local to xmpp proxy. Once started, it acts as both a local XMPP server your Jabber client can connect to and as a serverless XMPP client. With it, I am able to chat on the local network, even when our office is offline.
Installing it is easy from its git sources:
Now all that's left is adding a new account in your Jabber client. Choose a jabber id "username@localhost", disable SSL and allow plain text authentication on unencrypted connections. That's all.