The FreeBSD Diary

The way DCC Chat works often means it does notwork if  you are behind a firewall.   This is not the fault of the firewall, but rather it is a consequence of the DCC chat protocol.  The problem stems from the IP address translation which often occurs as the traffic passes through the firewall.  This translation is known as NAT or Network Address Translation.  The symptoms of the problem are an inability to send files with DCC but you are able to receive files.

To get around this problem, I've decided to try and install an IRC Proxy which will get around the problem.

The following is an extract from the man natd pages:

-use_sockets | -s
 Allocate a socket(2) in order to establish an FTP data or IRC
 DCC send connection.  This option uses more system resources,
 but guarantees successful connections when port numbers con­
 flict.

-same_ports | -m
 Try to keep the same port number when altering outgoing pack­
 ets.  With this option, protocols such as RPC will have a
 better chance of working.  If it is not possible to maintain
 the port number, it will be silently changed as per normal.

Try using these options to get your DCC to work.

I just thought I'd let you know in case you hadn't found out, natd aliases DCC connections if you are on port 6667 or 6668 of the IRC server.  So if you are connected to EFnet IRC Network or whichever network on either of those ports, DCC chat and sends should work (they do for me, ever since I've been using those ports).

Thanks David.