@lars_91: It's probably simpler than you think. Let JoyDS connect to your wifi router at first, run the JoyDS server, then DS-side enter in your computer's IP address. If you are not able to see a response after doing that, then I don't know.
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Currently running: NDSL: Unflashed (No FlashMe) Slot 1: Official R4 running Wood R4 1.27 Slot 2: eWin w/ Rudolph's GBA Loader v0.57 Roms: Untrimmed