Considering that online game playing traffic requires peer-to-peer connectivity (i.e. it requires UDP traffic to pass through from all destinations, and TCP traffic to all destinations from a host of ports), it is quite likely to get blocked by your firewall unless you have explicitly relaxed its ruleset.

This applies to all firewalls: regardless of whether it is a software firewall (such as the one that are now integrated in the later versions of Windows Operating Systems), a firewall that has been preloaded into your Broadband Internet Gateways' firmware, or a dedicated firewall router.

If you were able to setup and configure your WiFi USB adapter flawlessly but are unable to play games online with others, you may want to have a look at your firewall's ruleset.

Here is How to Determine if Your Gaming Traffic is being Blocked by a Firewall:

• Were you able to successfully install your USB Adapter on your PC? If so, it is quite likely that there are no networking issues (DHCP, IP address conflicts, NAT, DNS settings, default gateway setting, etc.) on your computer's LAN.
  
• Does you Nintendo DS detect your USB Connector or your Wireless AP? If so, it is more than likely that your USB connector (or your AP) is working fine and it is identifying itself as an Access Point.
  
• Were you presented with the Grant Permissions screen during the software installation process? If so, then the installation of your Nintendo DS WiFi USB Adapter Software was successful.
  
• Are you getting 52000, 53000, or 30000 series error codes on your Nintendo DS? One of the quickest way to determine if the traffic to and from your Nintendo DS WiFi USB Connector is being blocked by a firewall is to look at the error codes. If you are seeing error codes in the aforementioned ranges, it is more than likely that your gaming traffic is not getting past your firewall.

If you are able to establish the Nintendo Wi-Fi Connection, but unable to play games with others or if you are seeing error messages in the 52000, 53000, or 30000 range error message IDs; then you may have a potential issues with your computer's firewall.

Verify that your firewall is not blocking the protocols, and ports required for your Nintendo DS. If necessary, you may need to relax your firewall rules to:

• Allow TCP traffic to all destinations on ports: 28910, 29900, 29901, 29920, 80, and 443, and
  
• Allow UDP traffic (needed for allowing peer-to-peer connections for your game play) to all destinations.
  
• Alternatively, Specify your IP Blocks as Trusted IP Addresses: In stead of allowing UDP/TCP traffic from all sources, consider adding your IP address blocks to trusted IP addresses section of your computer's firewall. You would probably have to add something like: 192.168.1.1 (subnet mask 255.255.255.0 or 192.168.1.1/24), 172.16.1.1 (subnet mask 255.255.255.0 or 172.16.1.1/24), 0.0.0.0 and subnet mask 255.255.255.255 that your firewall should consider to be Trusted IP addresses.

Warning: Disabling/relaxing of firewall rules as listed above can significantly weaken your network security and make resources on your LAN more vulnerable to threats from the Internet. Please consult with a network security expert before disabling your firewalls and other network security measures.