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Re: [lwip-devel] TCP source port numbers

From: Kieran Mansley
Subject: Re: [lwip-devel] TCP source port numbers
Date: Mon, 11 Apr 2011 12:40:51 +0100

On Mon, 2011-04-11 at 13:31 +0200, Ullberg, Gustaf wrote:
> Excerpt from http://www.iana.org/assignments/port-numbers :
> "The Registered Ports are those from 1024 through 49151
> DCCP Registered ports SHOULD NOT be used without IANA registration.
> The registration procedure is defined in [RFC4340], Section 19.9.
> The Dynamic and/or Private Ports are those from 49152 through 65535"

I believe that is for listening ports, i.e. where you're running a
server that needs a well-defined port number so that the other end knows
where to contact it.  For the active open end of the connection the
source port is less restricted - try doing a connect (without a local
bind) on any Linux system for example and see what source port you get
given by the OS.  I'm pretty sure it will fall into the range you're
worried about.

I'm curious about why we have 4096 to 0x7fff in lwIP though.  1024 to
0xffff would make more sense to me.


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