Network Programming with Perl

Chapter 12. Multiplexed Applications

The forking and threading techniques discussed in the last two chapters allow a program to handle multiple concurrent connections. The last general technique that we cover is I/O multiplexing. Multiplexing doesn't take advantage of any operating system tricks to achieve the illusion of concurrency. Instead, multiplexed applications handle all connections in one main loop. For example, a server that is currently servicing ten clients reads from each connected socket in turn, handles the request, and then services the next client.

The big problem with interleaving I/O in this way is the risk of blocking. If you try to read from a socket that doesn't have data ready, the read() and sysread() calls will block ...