Chat between two Android smartphones

Suppose two people are on a plane, a few meters apart, with Android smartphones without internet access, and would like to communicate by text messages and if possible also by audio call, using Wifi or Bluetooth (both allowed on this plane). How can this be achieved? So far I have only been able to think of very complicated solutions, like using XMPP clients on the two phones, or Mumble clients on the two phones, setting up an XMPP server or a Mumble server on one of the phones, and communicating by Wifi, the main problem being that I haven't been able to find any XMPP or Mumble server for Android, so the only way out I have devised would be to install a Linux distro on one of the Android phones and inside of it, a standard XMPP or Mumble server. This is very heavy. Surely there must be easier solutions. Many thanks in advance.