If you use mIRC and windows xp firewall, you have noticed that dcc send won't work. Here is how to get it working without disabling the entire firewall :
1. First you must limit the range of port that mirc use in the Dcc, Option menu. In DCC ports , set both at 1024.
2. After, go into control panel & network connections
2. Right click on your connection and select 'properties'
3. Left click the advanced tab
4. Left click the settings button
5. Under services, left click the add button
6. For description type "DCC", for Name of IP put the name that identifies your system with your ISP OR your IP if it is static.
7. Both external and internal ports are 1024 by default and TCP.
8. Click OK and restart