use Net::Ping;
$p = Net::Ping->new(); print "$host is alive.\n" if $p->ping($host); $p->close();
$p = Net::Ping->new("icmp"); foreach $host (@host_array) { print "$host is "; print "NOT " unless $p->ping($host, 2); print "reachable.\n"; sleep(1); } $p->close(); $p = Net::Ping->new("tcp", 2); while ($stop_time > time()) { print "$host not reachable ", scalar(localtime()), "\n" unless $p->ping($host); sleep(300); } undef($p); # For backward compatibility print "$host is alive.\n" if pingecho($host);
You may choose one of three different protocols to use for the ping. With the ``tcp'' protocol the ping() method attempts to establish a connection to the remote host's echo port. If the connection is successfully established, the remote host is considered reachable. No data is actually echoed. This protocol does not require any special privileges but has higher overhead than the other two protocols.
Specifying the ``udp'' protocol causes the ping() method to send a udp packet to the remote host's echo port. If the echoed packet is received from the remote host and the received packet contains the same data as the packet that was sent, the remote host is considered reachable. This protocol does not require any special privileges.
If the ``icmp'' protocol is specified, the ping() method sends an icmp echo message to the remote host, which is what the UNIX ping program does. If the echoed message is received from the remote host and the echoed information is correct, the remote host is considered reachable. Specifying the ``icmp'' protocol requires that the program be run as root or that the program be setuid to root.
If a default timeout ($def_timeout) in seconds is provided, it is used when a timeout is not given to the ping() method (below). The timeout must be greater than 0 and the default, if not specified, is 5 seconds.
If the number of data bytes ($bytes) is given, that many data bytes
are included in the ping packet sent to the remote host. The number of
data bytes is ignored if the protocol is ``tcp''. The minimum (and
default) number of data bytes is 1 if the protocol is ``udp'' and 0
otherwise. The maximum number of data bytes that can be specified is
1024.
The icmp protocol requires that the program be run as root or that it be setuid to root. The tcp and udp protocols do not require special privileges, but not all network devices implement the echo protocol for tcp or udp.
Local hosts should normally respond to pings within milliseconds. However, on a very congested network it may take up to 3 seconds or longer to receive an echo packet from the remote host. If the timeout is set too low under these conditions, it will appear that the remote host is not reachable (which is almost the truth).
Reachability doesn't necessarily mean that the remote host is actually functioning beyond its ability to echo packets.
Because of a lack of anything better, this module uses its own routines to pack and unpack ICMP packets. It would be better for a separate module to be written which understands all of the different kinds of ICMP packets.