Re: UDP source port number when using RAW socket??

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Date: Mon, 28 Jun 2004 22:41:03 GMT

In article <f4178085.0406280235.6cd596d5@posting.google.com>,
Andreas <andreas_lindell76@hotmail.com> wrote:
>Hello Everyone
>
>I have created an application that runs as a client on a ADSL modem
>and communicates with a server on a Windows/MAC using as RAW socket
>with:
> sk = socket(PF_INET, SOCK_PACKET, htons(ETH_P_ALL));
>
>With this socket I can send RAW data to the server that listens on
>62828 . When I send I create my own ethernet, IP and UDP and send it
>out on my eth0 interface. This all works fine and my server receives
>the data correctly and responds. However now I have a question what
>number to assign to my source port number on UDP when creating my
>packet on the client??

Why are you bothering with raw packets if you're redoing all of the
work that the IP and UDP code does?

>So my question is:
>1) How do I get "hold" of a valid UDP port number that I can assign to
>my RAW packet?

Maintain the same list, like the UDP code does.

>2) Is there some sort of API I can call and if so what?

Probably not.

>3) What are the implications/problems if one for some reason have two
>applications sending out data on the same port number?

Depends on the protocol. If the other end uses the port you're sending
from as a place to send its data, you'll have to figure out how to
differentiate the two types of traffic. If the remote has a hardcoded
port that it sends to, then it doesn't matter what source port you
use.

-- 
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 Internet: steve @ Watt.COM                         Whois: SW32
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