dcc not working

Vernon Schryver vjs@calcite.rhyolite.com
Fri Jun 1 14:18:51 UTC 2007

> From: "Robert Welz" 

> I can't get dcc working. My email traffic is at about 3500 email/day so I
> choose the list as a last mean seeking for help.
> Can you help please, maybe I am blocked upstream somehow?

> 14:28:34.561453 IP Nausciaa.fixe-post.de.36172 > dcc.dmz.uncw.edu.
> 6277: UDP, length 40

What is the IP address of your DCC client?  I get NXDOMAIN when trying
to resolve the name Nausciaa.fixe-post.de from your tcpdump output.

The common part of the blacklists used by the public DCC servers
is visible at

] > This may be a stupid question but a starting point, but is the UDP Port
] > 6277 open outbound on your firewall?
] Yes, it is. I just verified that it is opened both inbound and outbound.

The common cause of such problems is blocking responses from UDP port
6277 at the distant DCC servers to you DCC client.  Your firewall must
allow outgoing packets to distant UDP port 6277 and responses from
distant UDP port 6277 to local ephemeral ports.  The DCC port 6277
should be treated like the DNS port 53.

How did you verify that your firewall is not blocking UDP port 6277?
Did you try `traceroute` with suitable initial UDP port numbers to
ensure that outgoing DCC requests are not being blocked?

] Do I have to reset dcc somehow? dcc tells me that it is waiting 1200
] seconds before next attempt.

The "skipping asking" timer in DCC clients is reset with the command
   cdcc rtt

Vernon Schryver    vjs@rhyolite.com

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