in reply to Check udp stream coming in

Yes, there are ways in Perl to automate this - now you just need to define what you are automating!

As moritz alluded to, you could open a pipe from the tcpdump command, parse the output from that command and do something with that.

Please be more specific about what you are trying to achieve, maybe show some sample output from the tcpdump command, and what the desired result is. The friendly Monks will be your, erm, friend.

Replies are listed 'Best First'.
Re^2: Check udp stream coming in
by shekarkcb (Beadle) on Oct 12, 2010 at 11:05 UTC
    Hi All,
    Thanks for the reply.

    Let me explain once again. I will be getting udp packets on my machine say 192.168.1.1 (eth1). I will verify this using
    tcpdump
    command. The output would look like this.

    tcpdump -i eth1 dst 225.1.1.152           
tcpdump: verbose output suppressed, use -v or -vv for full protocol de
+code
listening on eth1, link-type EN10MB (Ethernet), capture size 96 bytes 
+    
00:54:45.314015 IP 192.0.0.152.sieve > 225.1.1.152.sieve: UDP, length 
+1316
00:54:45.314234 IP 192.0.0.152.sieve > 225.1.1.152.sieve: UDP, length 
+1316
00:54:45.314580 IP 192.0.0.152.sieve > 225.1.1.152.sieve: UDP, length 
+1316
00:54:45.314768 IP 192.0.0.152.sieve > 225.1.1.152.sieve: UDP, length 
+1316

    [download]

    Now 'tcpdump' is a tool which can snif tcp/udp packets, to show that its is coming in properly. I can't every time login to system and run tcpdump and redirect the output to some file, parse the file, extract packet and see whether its fine or not. So i was thinking some script in Perl i can write to automate this. I don't want to use | (pipe) to tcpdump, get the output to a file etc. All i wanted to know is there any way in Perl to see packets are coming in to system? , say bind to system ip , listen for perticular port , check any data is coming in from destination ip etc(Some body told me about Socket programin, i thought i should try that before giving up on Perl). Since i am a newbie.. , Please guide me what kind of packages, tools do i need to use to achive this.
    Your help is appreciated...

    Thanks
[reply]
[d/l]
[select]
      What was being suggested was creating a script that would execute the tcpdump command for you, parse its output, and display whatever you want, based upon the results - no intermediate files, or anything. Without knowing what you are looking for, I can't specify an actual test for the desired output. 

      use strict;
use warnings;

open(my $tcp, "/usr/sbin/tcpdump |");
my $ok = undef;
while(<$tcp>) {
   $ok = 1 if m/\w/;   # your test here
}
print "All things groovy\n" if $ok;

      [download]
[reply]
[d/l]

In Section Seekers of Perl Wisdom