I have recently been taking an interest in <a href="http://vertx.io/">Vert.x</a> which allows you to write TCP Servers, HTTP Servers, SockJS Servers, etc ( it also allows you to write clients ). One thing to note is that it is built on top of Java 7 so it cannot be included in Android projects. So I started looking for a event based system for Android projects. ( I am a bit obsessed with the whole Event-Driven logic, if you couldn't already tell ).
After searching for a bit I found .... <a href="http://square.github.com/otto/">Otto</a>
I haven't had much time to play with the library but <a href="http://jakewharton.com/">Jake Wharton</a> makes really interesting stuff. Maybe someone can take a look at <a href="http://square.github.com/otto/">Otto</a> and let me know if it is as cool as it sounds.