You’ve come this far, and now you’re screaming for more! Where else can you go to learn more about all this stuff?
For old-school actual hold-it-in-your-hand pulp paper books, try some of the following excellent books. These redirect to affiliate links with a popular bookseller, giving me nice kickbacks. If you’re merely feeling generous, you can paypal a donation to beej@beej.us. :-)
Unix Network Programming, volumes 1-2 by W. Richard Stevens. Published by Addison-Wesley Professional and Prentice Hall. ISBNs for volumes 1-2: 978-013141155549, 978-013081081650.
Internetworking with TCP/IP, volume I by Douglas E. Comer. Published by Pearson. ISBN 978-013608530051.
TCP/IP Illustrated, volumes 1-3 by W. Richard Stevens and Gary R. Wright. Published by Addison Wesley. ISBNs for volumes 1, 2, and 3 (and a 3-volume set): 978-020163346752, 978-020163354253, 978-020163495254, (978-020177631755).
TCP/IP Network Administration by Craig Hunt. Published by O’Reilly & Associates, Inc. ISBN 978-059600297856.
Advanced Programming in the UNIX Environment by W. Richard Stevens. Published by Addison Wesley. ISBN 978-032163773457.
On the web:
BSD Sockets: A Quick And Dirty Primer58 (Unix system programming info, too!)
And here are some relevant Wikipedia pages:
Transmission Control Protocol (TCP)64
User Datagram Protocol (UDP)65
Serialization67 (packing and unpacking data)
RFCs68—the real dirt! These are documents that describe assigned numbers, programming APIs, and protocols that are used on the Internet. I’ve included links to a few of them here for your enjoyment, so grab a bucket of popcorn and put on your thinking cap:
RFC 169 —The First RFC; this gives you an idea of what the “Internet” was like just as it was coming to life, and an insight into how it was being designed from the ground up. (This RFC is completely obsolete, obviously!)
RFC 76870 —The User Datagram Protocol (UDP)
RFC 79171 —The Internet Protocol (IP)
RFC 79372 —The Transmission Control Protocol (TCP)
RFC 85473 —The Telnet Protocol
RFC 95974 —File Transfer Protocol (FTP)
RFC 135075 —The Trivial File Transfer Protocol (TFTP)
RFC 145976 —Internet Relay Chat Protocol (IRC)
RFC 191877 —Address Allocation for Private Internets
RFC 213178 —Dynamic Host Configuration Protocol (DHCP)
RFC 261679 —Hypertext Transfer Protocol (HTTP)
RFC 282180 —Simple Mail Transfer Protocol (SMTP)
RFC 333081 —Special-Use IPv4 Addresses
RFC 349382 —Basic Socket Interface Extensions for IPv6
RFC 354283 —Advanced Sockets Application Program Interface (API) for IPv6
RFC 384984 —IPv6 Address Prefix Reserved for Documentation
RFC 392085 —Extensible Messaging and Presence Protocol (XMPP)
RFC 397786 —Network News Transfer Protocol (NNTP)
RFC 419387 —Unique Local IPv6 Unicast Addresses
RFC 450688 —External Data Representation Standard (XDR)
The IETF has a nice online tool for searching and browsing RFCs89.