Subject: Re: IP-NAT and DCC
To: Andrew Brown <>
From: Guido Falsi +-|- <>
List: netbsd-users
Date: 05/07/1999 01:29:08
On 06-May-99 Andrew Brown wrote:
>>transfer, I think the port to which the person must connect is
>>specified in the dcc offer, so I don't think nat can guess it in any
>>easy way :-(
> the request itself travels over the irc connection between the irc
> client and the irc server.  so the endpoint of the server connection
> is "well known" (like ftp's command connection is well known), but not
> as well known as you might like it to be.  irc servers commonly run on
> ports 6665-6669, but there's absolutely nothing stopping anyone from
> running one on a completely different port.  the messages sent to the

Yes, I know that, and I'd add that thoose ports are the ones used by ircnet irc
servers, other irc network servers use others (common ones are 5555

> server from your client are:
>   NOTICE otherguy :DCC Send filename.txt (
>   PRIVMSG otherguy :^ADCC SEND filename.txt 3232239231 1054 477^A
> where the "privmsg" command is the important one.  that's the one that
> tells the remote client (the other guy) where to connect back to by
> specifying your address as a single, unsigned integer, then the port,
> and then some other number.  needless to say, dcc isn't covered in the
> irc rfc.  :)

I noticed that, this is beacause I didn't have any specific information ;-)

>>> on the port level, so I'm pretty much just guessing. I *think* not having
>>> a nailed-down port will be an issue, though.)
>>The problem is that dcc doesn't have any nailed down ports...
>, it doesn't.  and less so that ftp.  :)

well, not exactly, ftp has a well known port for the control connection, even
if the data connection is negotiated for evety transfer...And anyway ftp has
passive mode, about which I don't know anything, but it works throught

Guido Falsi +-|- <>