Re: Problem receiving UDP broadcast packets.

From	Grant Edwards <invalid@invalid.invalid>
Newsgroups	comp.lang.python
Subject	Re: Problem receiving UDP broadcast packets.
Date	2011-04-20 01:15 +0000
Organization	PANIX Public Access Internet and UNIX, NYC
Message-ID	<iolc32$luj$1@reader1.panix.com> (permalink)
References	(2 earlier) <iol5dm$rdb$2@reader1.panix.com> <4dae1d82$0$81483$e4fe514c@news.xs4all.nl> <mailman.592.1303257124.9059.python-list@python.org> <iol875$ah2$3@reader1.panix.com> <mailman.596.1303260785.9059.python-list@python.org>

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On 2011-04-20, Chris Angelico <rosuav@gmail.com> wrote:
> On Wed, Apr 20, 2011 at 10:09 AM, Grant Edwards <invalid@invalid.invalid> wrote:
>> The management program can then send another broadcast packet to
>> configure the IP address of a device. After that, the management
>> program switches over to normal unicast TCP and UDP protocols (HTTP,
>> TFTP, etc.) to set up the device.
>>
>
> Wonder if it would be possible to (ab)use DHCP for this. If every
> device registers itself with a central DHCP server, you could query
> that to find out what's around, and configuring of IP addresses would
> then be out of your hands.

I can't require the presense of a DHCP server, and many installations
won't have one.

> Or can you simply use a stupid netmask like /1 that picks up all the
> IP ranges? That way, the source-IP check wouldn't fail.

That would require that the device somehow knows that it's not
configured correctly and should change the netmask to /1.  The device
doesn't have any way to know that, and it must respond to the
discovery commands both before and after it's properly configured.

I've reread the protocol documentation and noticed that the device has
to respond not only to broadcasts to 255.255.255.255 but also to
subnet broadcasts send to subnets it's not on.  That pretty much
clinches the requirement to use a raw socket. :/

-- 
Grant

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Thread

Problem receiving UDP broadcast packets. Grant Edwards <invalid@invalid.invalid> - 2011-04-19 22:21 +0000
  Re: Problem receiving UDP broadcast packets. Irmen de Jong <irmen.NOSPAM@xs4all.nl> - 2011-04-20 01:13 +0200
    Re: Problem receiving UDP broadcast packets. Grant Edwards <invalid@invalid.invalid> - 2011-04-19 23:21 +0000
      Re: Problem receiving UDP broadcast packets. Irmen de Jong <irmen.NOSPAM@xs4all.nl> - 2011-04-20 01:40 +0200
        Re: Problem receiving UDP broadcast packets. Dan Stromberg <drsalists@gmail.com> - 2011-04-19 16:52 -0700
          Re: Problem receiving UDP broadcast packets. Grant Edwards <invalid@invalid.invalid> - 2011-04-20 00:09 +0000
            Re: Problem receiving UDP broadcast packets. Chris Angelico <rosuav@gmail.com> - 2011-04-20 10:53 +1000
              Re: Problem receiving UDP broadcast packets. Grant Edwards <invalid@invalid.invalid> - 2011-04-20 01:15 +0000
                Re: Problem receiving UDP broadcast packets. Chris Angelico <rosuav@gmail.com> - 2011-04-20 11:24 +1000
                Re: Problem receiving UDP broadcast packets. Grant Edwards <invalid@invalid.invalid> - 2011-04-20 03:05 +0000
                Re: Problem receiving UDP broadcast packets. Dan Stromberg <drsalists@gmail.com> - 2011-04-19 20:12 -0700
                Re: Problem receiving UDP broadcast packets. Grant Edwards <invalid@invalid.invalid> - 2011-04-20 14:31 +0000
                Re: Problem receiving UDP broadcast packets. Grant Edwards <invalid@invalid.invalid> - 2011-04-20 15:42 +0000
                Re: Problem receiving UDP broadcast packets. Dan Stromberg <drsalists@gmail.com> - 2011-04-19 20:16 -0700
                Re: Problem receiving UDP broadcast packets. Grant Edwards <invalid@invalid.invalid> - 2011-04-20 14:21 +0000
                Re: Problem receiving UDP broadcast packets. Dan Stromberg <drsalists@gmail.com> - 2011-04-20 18:35 -0700
                Re: Problem receiving UDP broadcast packets. Grant Edwards <invalid@invalid.invalid> - 2011-04-21 14:22 +0000
                Re: Problem receiving UDP broadcast packets. Heiko Wundram <modelnine@modelnine.org> - 2011-04-21 08:22 +0200
            Re: Problem receiving UDP broadcast packets. Roy Smith <roy@panix.com> - 2011-04-19 23:35 -0400
              Re: Problem receiving UDP broadcast packets. Grant Edwards <invalid@invalid.invalid> - 2011-04-20 14:23 +0000
            Re: Problem receiving UDP broadcast packets. Sherm Pendley <sherm.pendley@gmail.com> - 2011-04-20 06:07 -0400
              Re: Problem receiving UDP broadcast packets. Adam Tauno Williams <awilliam@whitemice.org> - 2011-04-20 06:20 -0400
                Re: Problem receiving UDP broadcast packets. Grant Edwards <invalid@invalid.invalid> - 2011-04-20 15:37 +0000
        Re: Problem receiving UDP broadcast packets. Grant Edwards <invalid@invalid.invalid> - 2011-04-19 23:54 +0000
          Re: Problem receiving UDP broadcast packets. Heiko Wundram <modelnine@modelnine.org> - 2011-04-20 08:45 +0200
            Re: Problem receiving UDP broadcast packets. Grant Edwards <invalid@invalid.invalid> - 2011-04-20 14:30 +0000
              Re: Problem receiving UDP broadcast packets. Heiko Wundram <modelnine@modelnine.org> - 2011-04-20 16:53 +0200
                Re: Problem receiving UDP broadcast packets. Grant Edwards <invalid@invalid.invalid> - 2011-04-20 15:24 +0000
                Re: Problem receiving UDP broadcast packets. Grant Edwards <invalid@invalid.invalid> - 2011-04-20 15:32 +0000
              Re: Problem receiving UDP broadcast packets. Grant Edwards <invalid@invalid.invalid> - 2011-04-20 15:50 +0000
  Re: Problem receiving UDP broadcast packets. Dan Stromberg <drsalists@gmail.com> - 2011-04-19 16:40 -0700
    Re: Problem receiving UDP broadcast packets. Grant Edwards <invalid@invalid.invalid> - 2011-04-20 00:00 +0000
      Re: Problem receiving UDP broadcast packets. Chris Angelico <rosuav@gmail.com> - 2011-04-20 10:32 +1000
  Re: Problem receiving UDP broadcast packets. Thomas Heller <theller@ctypes.org> - 2011-04-20 12:18 +0200
    Re: Problem receiving UDP broadcast packets. Grant Edwards <invalid@invalid.invalid> - 2011-04-20 14:35 +0000
  Re: Problem receiving UDP broadcast packets. Grant Edwards <invalid@invalid.invalid> - 2011-04-20 22:25 +0000

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