1.12 Summary
Figure 1.5 shows a
complete, albeit simple, TCP client that fetches the current time
and date from a specified server, and Figure 1.9 shows a
complete version of the server. These two examples introduce many
of the terms and concepts that are expanded on throughout the rest
of the book.
Our client was protocol-dependent on IPv4 and we
modified it to use IPv6 instead. But this just gave us another
protocol-dependent program. In Chapter 11, we will develop some
functions to let us write protocol-independent code, which will be
important as the Internet starts using IPv6.
Throughout the text, we will use the wrapper
functions developed in Section 1.4 to
reduce the size of our code, yet still check every function call
for an error return. Our wrapper functions all begin with a capital
letter.
The Single Unix Specification Version 3, known
by several other names and called simply The POSIX Specification by us, is the
confluence of two long-running standards efforts, finally drawn
together by The Austin Group.
Readers interested in the history of Unix
networking should consult [Salus 1994] for a description of Unix
history, and [Salus 1995] for the history of TCP/IP and the
Internet.
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