This is a guide and reference for network programming using the sockets and XTI (X/Open Transport Interface) APIs, and is based on the TCP/IP suite of protocols for IP v4 and v6. The book overviews client/server concepts, standards and functions before diving into the internals of the transport layer (TCP & UDP) states, buffer sizes and protocol usage. A large part of this publication (24 chapters) dissects sockets API programming.