Windows XP SP2 has an internal firewall that blocks P2P connections (if you don’t have SP2 installed you won’t have Windows Firewall installed). So we must configure Windows XP in order to “open” the ports used. If you have another firewall program installed such as ZoneAlarm or Norton Personal Firewall, you will need to make this procedure on your firewall program. After running your P2P program for the first time you probably unblocked it on Windows Firewall (by clicking on Unblock on the screen shown on Figure 5) but this isn’t enough.

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Figure 5: Windows asks you if you want to unblock your P2P program when you run it for the first time.

Open Control Panel, Windows Firewall and click on Exceptions tab. Your P2P program will probably be already listed there, as you can see on Figure 6, where eMule was already being listed. If not, click on Add program and choose your P2P program.

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Figure 6: Configuring Windows Firewall.

Even if your P2P program is already listed on Windows Firewall Exceptions tab you need to click on Add port. Then give a name to this rule (e.g. “eMule TCP Port”), add the TCP port number that eMule uses (4660), select “TCP” and click Ok (see Figure 7).

Figure 7: Adding the TCP port used by eMule.

Then click again on Add port, give a name to this rule (e.g. “eMule UDP Port”), add the UDP port number that eMule uses (4670), select “UDP” and click Ok (see Figure 8).

Figure 8: Adding the UDP port used by eMule.

These new rules will now be listed on Windows Firewall Exceptions tab, see Figure 9.

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Figure 9: Windows Firewall exceptions.

But that isn’t all. We still need to add one more configuration to Windows Firewall.