Unfortunately, I cannot recommend any books on the subject. People who write successful protocols spend their time maintaining successful implementations. People who write books about protocols have typically implemented protocols which are used within small niches, if at all.

If you want to learn by example then the best suggestion I can give is to read RFC821 (email delivery) ( http://www.faqs.org/rfcs/rfc821.html ), RFC822 (email headers) ( http://www.faqs.org/rfcs/rfc822.html ), RFC1094 (NFSv1) ( http://www.faqs.org/rfcs/rfc1094.html ), RFC1813 (NFSv3) ( http://www.faqs.org/rfcs/rfc1813.html ), RFC3010 (NFSv4) ( http://www.faqs.org/rfcs/rfc3010.html ), RFC1436 (Gopher protocol) ( http://www.faqs.org/rfcs/rfc1436.html ), RFC1459 (IRC protocol) ( http://www.faqs.org/rfcs/rfc1459.html ), RFC1945 (HTTP/1.0) ( http://www.faqs.org/rfcs/rfc1945.html ), RFC2616 (HTTP/1.1) ( http://www.faqs.org/rfcs/rfc2616.html ) and supporting documents for a mix of text and binary protocol specifications, reasonings and evolutions.

If you're not accustomed to reading RFCs then they may seem quite terse. Persevere and it will get easier after the first five or so. At the very least, read RFC822 because it is the basis of web and email headers.