how to catch ICMP unreachable within UDP sendto

  1 use strict;
  2 use warnings;
  3 use IO::Socket::INET;
  4
  5 my $cl = IO::Socket::INET->new(
  6     PeerAddr => '192.168.178.1:12345', # definitly rejecting
  7     Proto => 'udp',
  8 );
  9 $cl->send('foo') or die "send failed: $!"; # first send will succeed
 10 # wait some time to receive ICMP unreachable
 11 sleep(1);
 12 $cl->send('bar') or die "send failed: $!"; # will fail
-------
$ perl a.pl
send failed: Connection refused at a.pl line 12.
-------
$ strace -e sendto perl a.pl
sendto(3, "foo", 3, 0, NULL, 0)         = 3
sendto(3, "bar", 3, 0, NULL, 0)         = -1 ECONNREFUSED (Connection refused)
------
# tcpdump -i $if -n udp or icmp
18:35:43.810818 IP 192.168.178.4.54762 > 192.168.178.1.12345: UDP, length 3
18:35:43.812406 IP 192.168.178.1 > 192.168.178.4: ICMP 192.168.178.1 udp port 12345 unreachable, length 39