OK long story short I have a UDP listener using IO::Socket::INET that I am trying to grab the first 4 bytes from the data with a pattern match that is failing on roughly 1 out of 100 packets. First here is my simplified code:

#!/usr/bin/perl -w
$|++;
use strict;
use IO::Socket;
use IO::Select;

my $response = IO::Socket::INET->new(Proto=>"udp",LocalPort=>5000)
  or die "Can't make UDP server: $@";

my $sel = new IO::Select( $response );

my ($datagram,$flags);

binmode($response);

while(my @ready = $sel->can_read) #Make sure socket has something to g
+ive us
{
  $datagram = '';
  $flags = '';
  $response->recv($datagram,1500,$flags);
  my $length = length($datagram);
  print "Length : $length\n";
  if($datagram =~ /^(\C\C\C\C)(.*)$/s)
  {
    #Do some stuff
  }
  else
  {
    #Didn't match for some reason
    print "Did not match!\n";
  }
}

[download]

Here is the root of my question: I print out the length of the packet just prior to attempting the pattern match, which always has a length of "1205", but when I attempt the match with $datagram =~ /^(\C\C\C\C)(.*)$/s it sometimes fails. How can this match fail (which I believe is just looking for the first 4 bytes in the datagram) when the data is 1205 bytes long?

Oh, and here is a snipet of the output:

Length : 1205
Length : 1205
Length : 1205
Length : 1205
Length : 1205
Did not match!
Length : 1205
Length : 1205

[download]

Any guidance would be greatly appreciated! :)

In reply to Pattern match not working sometimes by dantheman1210

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