Network Programming with Perl

Chapter 13. Nonblocking I/O

By default, on most operating systems I/O is blocking. If a request to read or write some data can't be satisfied immediately, the operating system puts the program to sleep until the call completes or generates an error. For most programming tasks, this does not cause a problem, because disk drives, terminal windows, and other I/O devices are relatively fast, at least in human terms. As we saw in the last chapter, however, blocking presents a problem for client/server programming because a single blocked network call can make the whole program hang while other requests wait.

To mitigate the effect of blocking in read or write calls, one can either have several concurrent threads of execution, as with forking and ...