TCP/IP Networking

The books by Comer are well-written; they are the standard descriptions of the TCP/IP protocols. The books by Stevens are also very highly regarded.

Internetworking with TCP/IP: Principles, Protocols, and Architecture , Third Edition, Douglas E. Comer, Prentice-Hall, Englewood Cliffs, NJ, USA, 1995. ISBN: 0-13-216987-8.
Internetworking With TCP/IP: Design, Implementation, and Internals , Third Edition, Douglas E. Comer and David L. Stevens, Prentice-Hall, Englewood Cliffs, NJ, USA, 1998. ISBN: 0-13-973843-6.
Internetworking With TCP/IP: Client-Server Programming and Applications: BSD Socket Version , Second Edition, Douglas E. Comer and David L. Stevens, Prentice-Hall, Englewood Cliffs, NJ, USA, 1996. ISBN: 0-13-260969-X.
Internetworking With TCP/IP: Client-Server Programming and Applications: AT&T TLI Version , Douglas E. Comer and David L. Stevens, Prentice-Hall, Englewood Cliffs, NJ, USA, 1993. ISBN: 0-13-474230-3.
TCP/IP Illustrated, Volume 1: The Protocols , W. Richard Stevens, Addison Wesley Longman, Reading, MA, USA, 1994. ISBN: 0-201-63346-9.
TCP/IP Illustrated, Volume 2: The Implementation , W. Richard Stevens and Gary R. Wright, Addison Wesley Longman, Reading, MA, USA, 1995. ISBN: 0-201-63354-X.
TCP/IP Illustrated, Volume 3: TCP for Transactions, HTTP, NNTP, and the Unix Domain Protocols , W. Richard Stevens, Addison Wesley Longman, Reading, MA, USA, 1996. ISBN: 0-201-63495-3.
Unix Network Programming, Volume 1: Networking APIs: Sockets and XTI , W. Richard Stevens, Prentice-Hall, Englewood Cliffs, NJ, USA, 1997. ISBN: 0-13-490012-X.
Unix Network Programming, Volume 2: Interprocess Communications , W. Richard Stevens, Prentice-Hall, Englewood Cliffs, NJ, USA, 1998. ISBN: 0-13-081081-9.

This volume and the previous one are revisions of the first edition that was the standard book on Unix network programming for many years.
Unix System V Network Programming , Steven A. Rago, Addison Wesley Longman, Reading, MA, USA, 1993. ISBN: 0-201-56318-5.