Designing an application protocol [closed]

Question

I have an existing standalone application which is going to be extended by a 3rd-party, using a network protocol. The capabilities are already implemented, all I need is to expose them to the outside.

Assuming the transport protocol is already chosen (UDP), are there any resources that will help me to design my application protocol?

There seems to be a lot of information about software design, but not on protocol design. I've already looked at Application Protocol Design.

Answer 1

See Jabber protocols design guidelines and RFC 4101. Although it is aimed at making RFCs more easy to understand to reviewers, this RFC provides some interesting advices.