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[NMaestroJ]

Does anyone know of a specific reason why I can log onto wifi just fine, but when I go to battle someone, the one who's trying to join the battle (whether it's me or the other person) gets knocked offline?

 

[Enygma]

Does anyone know of a specific reason why I can log onto wifi just fine, but when I go to battle someone, the one who's trying to join the battle (whether it's me or the other person) gets knocked offline?

EDIT:
Possible Error Codes

Unable to Connect to Other Players

• ^ This information seems to be the most helpful for you right now.

Thanks. I just got this damn router today...

Updated my previous post. Apparently I was a bit incorrect. It has nothing to do with the firmware, but rather the router's Firewall. Since you just recently obtained it, perhaps you did not set the Firewall properly to be able to send/receive some information required to interact with other players. Try fiddling with your Firewall settings.

Make sure you are correctly attempting to connect with other players (click here and select the game you are playing). If you are able to connect to the Nintendo Wi-Fi Connection, but are still unable to connect with other players (including receiving error messages in the 80000-89999 range), our experience shows that problems encountered at this point are likely caused by a firewall. Firewalls regulate traffic coming into, and going out from, your home network. They also control which "ports" on your networked devices are allowed to send and receive traffic, and they can interfere with certain types of data packets necessary for "Friend" play. The firewall compatibility problem may be occuring on your end, or on the player(s) you are attempting to connect to. (This is true even if you are able to connect to some players, but not with others, or others are unable to connect with each other but not with you). Please click here to read more about firewalls, as well as possible solutions.

If you are unable to connect to the Nintendo Wi-Fi Connection after successfully connecting to your access point (this includes error messages in the 50000-59999 range) our experience shows that problems encountered at this point are likely caused by your wireless router's built-in firewall protection. Firewalls regulate traffic coming into, and going out from, your home network. They also control which "ports" on your networked devices are allowed to send and receive traffic. These factors can interfere with a successful or sustained connection with the Nintendo Wi-Fi Connection. Please click here to read more about firewalls, as well as possible solutions.

 

[Sixfortyfive]

Does anyone know of a specific reason why I can log onto wifi just fine, but when I go to battle someone, the one who's trying to join the battle (whether it's me or the other person) gets knocked offline?

Assign your DS a static IP, and put this IP address in your router's DMZ if you can. This is effectively the same as opening all of the ports for your DS.