Kevin McAllister on 7 Jan 2012 08:19:01 -0800

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Re: [PLUG] Need Help with TCPDump

Seems odd, is eth1 where you expect the packets to have the destination internal address?

Also you should you try sniffing on boot of clock? The clock must be registering with the external service and maintaining a persistent connection to receive messages. 

On Jan 7, 2012, at 10:41 AM, wrote:

> I bought one of those goofy internet clocks ( and 
> despite a few problems, have been able to get my messages sent to it via the 
> company's web page or eMail.
> However, being one who will never leave anything working alone (I have an 
> unsatisfiable desire to "improve" things! <grin>), I want to hack this little 
> bad boy.
> I have not found anything published on the protocol for the clock, so I 
> thought I'd just sniff the network stream and  figure out what it's doing.  I 
> can tell from my DHCP server that it's getting a lease at  I 
> therefore tried this command on my firewall.
> tcpdump -i eth1 host
> I then used the web page to successfully send a message to the clock.
> Oddly, I'm not getting anything recorded by tcpdump.  If I drop the host 
> portion and just grab everything, the address of the clock never shows up.
> Could somebody suggest what I'm doing wrong, or some other approach that might 
> let me figure out how this thing communicates?
> Ideally, I want to be able to directly send messages to the clock, without 
> using the company's web service.
> -- 
> Casey Bralla
> Chief Nerd in Residence
> The NerdWorld Organization
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