Learning Perl on Win32 Systems

Getting Network Information

Perl supports network programming in a way that is very familiar to those who have written network code in C programs. In fact, most of the Perl functions that provide network access have the same names and similar parameters as their C counterparts. We can’t teach a complete course on network programming in this chapter, but let’s take a look at one of the task fragments to see how it’s done in Perl.

One of the things you need to find out is the network address that goes with a network name, or vice versa. In C, you use the gethostbyname routine to convert a network name to a network address. You then use this address to create a connection from your program to another program somewhere else.

The Perl function to translate a host name to an address has the same name and similar parameters as the C routine, and looks like this:

($name, $aliases, $addrtype, $length, @addrs) =
		gethostbyname($name); # generic form of gethostbyname

The parameter to this function is a hostname—for example, slate.bedrock.com. The return value is a list of four or more parameters, depending on how many addresses are associated with the name. If the hostname is not valid, the function returns an empty list.

If gethostbyname is called in a scalar context, only the (first) address is returned.

When gethostbyname()completes successfully, $name is the canonical name, which differs from the input name if the input name is an alias. $aliases is a list of space-separated names by which ...