The paper describes a methodology for the implementation of structured, networking software. The particular communication protocol to be implemented is first defined in the form of an extended event/state-transition table. This is effectively a tabular representation of the state transitions associated with the protocol but extended to include the corresponding actions to be performed at each transition. This naturally leads to a precise and readily understood definition of the protocol which can readily be implemented using a structured procedural language. As an example of the use of the methodology, the paper also describes the implementation details of a networking package for a small floppy-disc-based single-user computer system based on the X25 standard protocol