Perl in a Nutshell, 2nd Edition

Chapter 15. Sockets

Why build networking functionality into your Perl scripts? You might want to access your email remotely, or write a simple script that updates files on an FTP site . You might want to check up on your employees with a program that searches for Usenet postings that came from your site. You might want to check a web site for any recent changes, or even write your own home-grown web server. The network is the computer these days, and Perl makes network applications easy.

Perl programmers have their choice of modules for doing common tasks with network protocols; Chapter 14 through Chapter 17 cover the modules for writing email, news, FTP, and web applications in Perl. If you can do what you want with the available modules, you’re encouraged to jump to those chapters and skip this one. However, there will be times when you’ll have to wrestle with sockets directly, and that’s when this chapter comes in.

Sockets are the underlying mechanism for networking on the Internet. With sockets, one application (a server) sits on a port waiting for connections. Another application (the client) connects to that port and says hello; then the client and server have a chat. Their actual conversation is done with whatever protocol they choose—for example, a web client and server would use HTTP, an email server would use POP3 and SMTP, etc. But at the most basic level, you might say that all network programming comes down to opening a socket, reading and writing data, and closing the ...