A computer must have netcat binary to communicate with this application. For Linux/MacOS it's a "nc" binary usually. This file is included in "netcat-openbsd" or "netcat-traditional" Ubuntu packages.
There is no prebuild standard netcat for Windows. Windows users can use "go-netcat" application - http://dl.bintray.com/dddpaul/generic/gonc/. It's my netcat implementation written in Go and it's sources are hosted on Github - https://github.com/dddpaul/gonc.
Simple NetCat sources are hosted on Github too. See https://github.com/dddpaul/android-SimpleNetCat for full information and examples.