[K12OSN] Reading TCP packets

Nils Breunese nils at breun.nl
Wed Jul 23 17:47:58 UTC 2008

Sudev Barar wrote:

> 2008/7/23 "Terrell Prudé Jr." <microman at cmosnetworks.com>:
>>> I have a remote device that is generating data and is sending as a  
>>> TCP
>>> packet to designated IP:Port. If I open and set a non standard  
>>> port I
>>> am able to receive the packets using a listener. Problem is that the
>>> host where I have to move this project allows listening only on port
>>> 80 (apache) or port 25/110 (mail) or port 22 (ssh)
>>> How can I set up apache or iptables to log in incoming data packets
>>> while at the same time allow apache to serve web pages?
>>> My google time continues to turn up inconclusive leads.
>> If you're sniffing, which is what it sounds like you're doing, then  
>> it
>> doesn't matter which "port you have open."  You don't need to have  
>> any
>> "ports open" on your sniffer.  Rob Owens suggested Wireshark, and I
>> agree with him.  TCPDump is another good sniffer.
> No I am not sniffing. The remote device can be set to send packets to
> any IP:Port combination. So I just opened a random high port in my
> firewall and used "nc" to read the packets at that port. Then another
> program takes over and process these and log them on to database.
> Now problem is after establishing proof of concept on my laptop I need
> to run this system on a web-host and that host only has ports
> mentioned open.

I don't know what kind of 'remote device' you're talking about, but  
can't that device make HTTP requests? If so, you could set up a web  
service on the web host and have that handle the messages. If SSH is  
supported you could also have the 'remote device' run a command on the  
web host via SSH. The third option seems to let the 'remote device'  
send an e-mail, as SMTP is also open. :o)


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