Making use of pcap for sending and receiving network packets and (py)construct for parsing and building, Neprottest is a nice piece of software to help you in your work with python. Can be used for building simple (or not so simple) packet sniffers such as wireshark. Test and see if your new router correctly supports a certain standard as the supplier claims. Implement, simulate and test your custom or existing protocols. Test security features or your network administrator's patience. All that and more with Neprottest.