Thank you for your prompt reply. I'll give it a try.

Thank you for your continued support.
I followed the advice I received, but it didn’t work.
The steps I took are as follows:

Connected the tablets via WiFi-Direct Registered NSD on each tablet Confirmed the registration via logs
Attempted a WebRTC video call (no candidates appeared in the connection process...)

I used the Flutter plugin "nsd:3.0.0" for NSD registration. The registration process is as follows:

code:
final registration = await register(const Service(name: 'test', type: '_http._tcp', port: 8080));
print("[NSD check] name = ${registration.service.name}");
print("[NSD check] type = ${registration.service.type}");
print("[NSD check] port = ${registration.service.port}");

Log:
2024-09-11 17:52:13.509 16795-16841 flutter com.example.base I [NSD check] name = test
2024-09-11 17:52:13.509 16795-16841 flutter com.example.base I [NSD check] type = _http._tcp
2024-09-11 17:52:13.509 16795-16841 flutter com.example.base I [NSD check] port = 8080

Is it still impossible to establish a connection even when using NSD?
Or is there a mistake in the way I’m implementing it?

I think NSD just announces that you have a service on port 8080. I guess you actually need to write a dart http server or websocket server to listen on port 8080 so that another client that discovers this service can establish a real http/ws connection.

Thank you again for your continuous advice.

As you pointed out, I was connected to both Wi-Fi Direct and WebSocket at the same time.
Afterward, I had registered with SND, so after connecting to Wi-Fi Direct,
I will try to register the SND service and then establish a WebSocket connection based on the registered service.

Thank you for the advice you provided the other day.
Following your suggestion, I registered with NSD and then connected via WebSocket.
After that, I attempted communication using WebRTC, but the connection failed.

After connecting via WiFi-Direct, I checked whether I could obtain the IP address using network_info_plus,
but the result was null. (When connected to a regular WiFi network, it returns a value.)

I suspect that the information defined by NSD is set on the WiFi-Direct side, and WebRTC is unable to access it.
What do you think? Do you have any ideas on how to resolve this?