Chapter 48. Net::Telnet
This article introduces Net::Telnet, a module that allows your Perl program to communicate with networked hosts or devices such as workstations, terminal servers, routers, and the like. The dialog is established via a client connection to a TCP port—typically, to a port using the
Simple I/O methods such as
print, get, and
getline are provided, of course, but more sophisticated interactive features are available as well—features tailored for communicating with programs intended solely for human interaction. This includes the ability to specify a timeout and to wait for a pattern to appear in the input stream, such as a shell prompt.
Net::Telnet is written entirely in Perl; it doesn’t require a locally installed
telnet program. This makes Net::Telnet especially easy to install and use on those ubiquitous Windows machines.
Sounded easy when you first thought about it: your Perl program needs to monitor disk space on a remote machine named
sparky, but it can access
sparky only by connecting to it via
telnet. You try something like this:
open TELNET, "|telnet sparky"; print TELNET "joebob\n"; print TELNET "passwd-for-joebob\n"; print TELNET "df -k\n";
You find that piping commands to
telnet’s standard input doesn’t work. The
telnet program connects just fine, but
sparky doesn’t process any of the commands you send it. You discover that your
telnet only reads from the terminal (also known as a tty ) and not from its standard input. ...