Are there any open source, high level tools that would facilitate and simplify development of experimental network protocols (TCP/UDP) using a GUI?
Basically, something like a dynamic state machine editor that would allow you to define "packets", "messages", "states", "validators", "handlers" etc.
Preferably, such a tool would be comprehensive enough to deal with all relevant aspect of the protocol (i.e. client & server), so that the high level protocol description could be serialized out to an XML/RDF file where it could be used to dynamically create application code to implement the protocol (i.e. in Python).
Give up the GUI for a text editor and enter the world of protocol specification languages. Most of these tools take a description of some protocol, try to prove it's not broken, and generate an implementation and tests. Here's a few to get you started, but there's many more: