[Twisted-Python] Change A UDP based server to TCP based

Hi all, I found twisted have a module called SIP which implements parts of RFC3261, Session Initial Protocol. As I am going to write an experimental SIP server, this module seems to be very useful for me. But, one problem : it's based on UDP. I skimmed the code and I think maybe I can "Cut and Copy" some code of this module to implement my own TCP SIP server. But the idea of "cut and copy" is really annoying. What will you do in my situation? BTW, if you are going to write a protocol which supports both UDP and TCP, what is your design going to be like?