Test multiplayer LAN

[albanox9]

What version of melonDS DS are you using?

1.20

Does the problem happen in standalone melonDS?

I don't know.

What happened?

Summary

I have successfully tested local wireless multiplayer using the melonDS-DS core in RetroArch (v1.21) on Android between two smartphones. The game used was New Super Mario Bros. DS (EUR), specifically the multiplayer minigames.

However, when attempting to add a third player (running RetroArch on a PC), the emulator freezes or becomes unresponsive. This makes 3-player local wireless play impossible in the current state of the melonDS-DS core (v1.20).

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Test Environment

Devices Used:

• Device 1 (host + hotspot): Samsung Galaxy S23+ – Android 14
• Device 2 (client): Samsung Galaxy A52 – Android 14
• Device 3 (failing client): PC running RetroArch 1.21 (Windows 10)

RetroArch Version (all): 1.21
melonDS-DS Core Version (all): 1.20
Game Tested: New Super Mario Bros. DS (EUR)
BIOS/firmware: Real DS BIOS and firmware used across all devices

Network Setup:

• The Galaxy S23+ created a hotspot (mobile data enabled).
• Both the A52 and the PC connected to that hotspot.
• All three RetroArch instances used the same core and ROM.

Core Settings:

• Use external BIOS: ON
• Boot from firmware: ON
• Enable WiFi: ON (if applicable)

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Behavior with 2 Players (S23+ and A52)

• The host creates a local wireless room inside the minigames menu.
• The second Android device detects and joins the session successfully.
• Gameplay is smooth and stable with no latency or desync.
• Notably, using a mobile hotspot (with mobile data ON) gives significantly more stable performance than standard WiFi.

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Problem with 3 Players (adding PC client)

• When the PC attempts to join the same session:
  • RetroArch freezes immediately upon detection or connection attempt.
  • Occasionally, it also causes the other clients to freeze.
  • The emulator must be force-closed; no recovery is possible.
• No error logs or crash messages appear.

This suggests a hard-coded limitation or lack of handling for a third simultaneous WiFi client in the melonDS-DS core.

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Expected Behavior

Ideally, the core should:

• Support 3+ players in local multiplayer, as the original DS hardware did, or
• At least reject additional clients gracefully without crashing any instance.

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Suggestion

Please consider:

• Clarifying in the documentation that 2-player multiplayer is the current max supported,
• Adding protections to prevent full emulator crashes when a third device joins,
• Exploring future support for 3+ clients if technically feasible within the libretro core.

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Additional Notes

We’re aware the standalone melonDS emulator on PC allows experimental LAN multiplayer with 3+ devices using manual IP setup. If similar logic can be implemented in the libretro core, it would allow RetroArch users to emulate a full DS wireless experience.

Thanks for the hard work — having two-player DS wireless working on Android is already a fantastic feature!

What should've happened instead?

The core should have handled a third WiFi peer gracefully, either by supporting the connection or by rejecting it cleanly without causing the emulator to become unresponsive

Which platforms do you see the problem on?

• Windows
• macOS
• Linux
• Android
• iOS
• tvOS
• Other (specify below)

Which versions of the OS?

Android 15

Which libretro frontend are you using?

1.21

Terms

• I agree to follow the code of conduct.
• I understand that melonDS DS is not developed or maintained by the authors of melonDS.
• I understand that this form is for reporting bugs, not for requesting help.
• I understand that the author develops this core in his spare time, and that he is under no obligation to respond to this bug report.

[BernardoGomesNegri]

Did you set up MAC addresses correctly? See the documentation.