in reply to Intercepting UDP broadcasts

Do have a firewall on the box you're testing on? That might explain why tcpdump can see the packets, but your code can't.

-sam

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Re: Intercepting UDP broadcasts
by Abigail-II (Bishop) on Jan 30, 2004 at 19:53 UTC
    Nope. No firewall on the box. There's nothing special running on the box - a plain Redhat 7.3 distro.

    I'll have to think it over during the weekend - I won't be back in the office to work on it till Monday.

    Abigail

[reply]
      By default (unless you asked for "no security" or something similar during the install) RH7.3 sets up an ipchains firewall which will block incoming UDP packets for port <= 1023, among others. Is there any chance that's tripping you up?
[reply]
        Sounds like AM has a good idea here.. check your kernel log to see if they got dropped. I used your code on the OP and 'nc -u localhost 67' and it worked like a charm. "foobar.\n" => Saw a bootp request


        mhoward - at - hattmoward.org
[reply]
        Actually it leaves it on no matter what choice you make during install on all the 7.x and 8.x versions. I always had to go in and diable it for Oracle. I think they finally fixed it in 9, but I've since switched to Gentoo and haven't installed RH in a while.

        As for examples, the last broadcast UDP client I saw was the Net::mDNS module that is used to send and receive multicast dns over udp for things like Apple's Rendezvous. You can get it from CPAN.

        HTH
[reply]

      After reading some more 'nix socket threads you might want to try binding to 0.0.0.0 instead of 255.255.255.255

      coreolyn
[reply]

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