Okay, there are the books you need:
"Advanced Programming in the UNIX Environment"
by W. Richard Stevens 1992 Addison-Wesley
ISBN 0-201-56317-7
"TCP/IP Illustrated Volume 2"
by Gary R. Wright, W. Richard Stevens 1995 Addison-Wesley
ISBN 0-201-63354-X
"UNIX Network Programming Volume 1"
by W. Richard Stevens 1998 Addison-Wesley
ISBN 0-13-490012-X
"UNIX Network Programming Volume 2"
by W. Richard Stevens 1999 Addison-Wesley
ISBN 0-13-081081-9
Unfortunately, the author (Stevens) was killed in a car crash a year or two ago, so this former font of practical information is no more.
Cheers