Programming Python, 3rd Edition

Rolling Your Own Servers in Python

Most of the Internet modules we looked at in the last few chapters deal with client-side interfaces such as FTP and Post Office Protocol (POP), or special server-side protocols such as CGI that hide the underlying server itself. If you want to build servers in Python by hand, you can do so either manually or by using higher-level tools.

Standard Library Socket Servers

We explored the sort of code needed to build servers manually in Chapter 13. Python programs typically implement servers either by using raw socket calls with threads, forks, or selects to handle clients in parallel, or by using the standard library SocketServer module. As we learned earlier, this module supports TCP and UDP sockets, in threading and forking flavors; you provide a class method invoked to communicate with clients.

Whether clients are handled manually or with Python classes, to serve requests made in terms of higher-level protocols such as FTP, the Network News Transfer Protocol (NNTP), and HTTP, you must listen on the protocol’s port and add appropriate code to handle the protocol’s message conventions. If you go this route, the client-side protocol modules in Python’s standard library can help you understand the message conventions used.

You may also be able to uncover protocol server examples in the Demos and Tools directories of the Python source distribution and on the Net at large (search http://www.python.org or do a general web search). See prior chapters ...