Blaubot
Blaubot is a middleware to create small adhoc networks via P2P connections such as Bluetooth-RFCOMM, Adhoc-WiFi or simple socket connections. Blaubot takes care of device discovery and connection establishment with the goal to minimize a developer's boilerplate code to set up these small networks.
Tl;dr our main goal is to let a developer call start();
and spare him as much hassle as possible to create ad hoc networks. Blaubot is written in Java and has a dedicated version for Android (blaubot-android).
The documentation and a quick start guide can be found on the project site.
If you want to just want to use Blaubot, please check the project site. You don't need to check out the whole project for that. Instead grab a release from Bintray or MavenCentral as explained on the website.