perl listen to a port number to check status

Question

I have a daemon, for which, I need to check the status and see if it is up or down. As of now, I am using an expect script to telnet to the port and see if it is alive. I am looking to rewrite it in perl, to check the same. Any pointers to modules or features that I can use is greatly appreciated.

Answer 1

http://metacpan.org/pod/IO::Socket::PortState would be a good place to start. There might be better solutions, but this is what I am using.

Answer 2

For quickly checking a single port, Net::EmptyPort provides check_port, or it's simple enough to do it yourself with IO::Socket::IP. Both are less hassle than using IO::Socket::PortState for just one port (which describes its own interface as “complex”).

With Net::EmptyPort:

use Net::EmptyPort qw<check_port>;

if (check_port 5432)
{
    # ...
}

But if you look at what that's doing, you may decide you can as easily make the socket connection yourself, along the lines of:

use IO::Socket::IP;

my $socket = IO::Socket::IP->new(PeerAddr => 'localhost', PeerPort => 5432);
if ($socket)
{
  $socket->close;
  # ...
}

That also lets you provide other arguments, such as Timeout to adjust how long it waits before giving up and deciding that the port isn't in use. For localhost you may be able to get away with a much shorter time-out than the default; I've used 100 ms without problem.