[Help] Cannot read from device, but can write to it

Mobile Device Environment Provide a list of operating systems on which this issue is relevant.

• Device: Android
• OS: Android 11

Application Environment Provide information about your development environment:

• React Native version: v0.63.4
• RN Bluetooth Classic version: 1.60.0-rc.16

Describe the bug I have a Raspberry Pi 3, on which a bluetooth server (Bluedot btcomm) is running. I can send and receive data perfectly from the Android Serial Bluetooth Terminal application. But with my React Native app, I can only send data. I cannot read data from the device. My code is shown below:

  let status = await RNBluetoothClassic.requestBluetoothEnabled();
  if (status) {
    try {
      let unpaired = await RNBluetoothClassic.startDiscovery();
      let rpi = unpaired.find((o) => o.name === "raspberrypi");
      if (rpi) {
        let conn = await RNBluetoothClassic.getBondedDevices();
        let connStatus = conn.find((o) => o.name === "raspberrypi");
        if (!connStatus) {
          console.log("Pairing....");
          await RNBluetoothClassic.pairDevice(rpi.id);
        }
        try {
          device =  await RNBluetoothClassic.connectToDevice(rpi.id, {});
          await device.connect({});
          await device.write("Foo", "ascii");  // 'Foo' is received in raspberry pi
          console.log(await device.available());  // Logs '0'
          await device.onDataReceived((res) => console.log(res));  // Does not log anything
          let readData = await device.read();
          console.log(readData);  // Logs 'null'
        } catch (e) {
          console.log(e);
        }
      } else {
        console.log("Bluetooth error!");
      }
    } catch (e) {
      console.log(e);
    }
  }

Please let me know if I am doing anything incorrectly.

Thank you.

[deepalisrivastava25]

@hemanth-kumarv @kenjdavidson I have implemented this library in my app to establish bluetooth connection with another device.(which is an android phone in my case) However I am unable to connect to another device. In the above code snippet shared by @hemanth-kumarv , device = await RNBluetoothClassic.connectToDevice(rpi.id, {}); await device.connect({});

connectToDevice accepts 2 params which are address and options.

This is the definition of this method in the react-native-bluetooth-classic lib.

connectToDevice(address, options) {
    return __awaiter(this, void 0, void 0, function* () {
        // Comming from the Java world this is nuts - not being able to assign anything to
        // options because it's a <T extends StandardOptions> even with something that matches
        // the StandardOptions interface
        let connected = yield this._nativeModule.connectToDevice(address, options || {});
        return new BluetoothDevice(connected, this);
    });
}

What do we mean by the comment section above.? What should I pass as options in connectToDevice method.

Can you share a proper example of how can we connect to a device?

[kenjdavidson]

Not sure what to tell ya man, the error is right there

Error: java.io.IOException: read failed, socket might closed or timeout, read ret: -1

The socket on the other side (ServerSocket) is:

• closed
• timeout
• etc

as I mentioned before, in order to make a connection, you need something waiting on the other side to accept this connection.

• How are you doing that?
• You say that accept doesn’t work, but how doesn’t it work? you have provided no errors.

You also need to have an understanding of the language used:

• Paired = Paired
• Connected = RFCOMM socket open

You’re not connected (ie. the error above) so you’d never get the device back from isDeviceConnected(). I can tell you that the accept method works just fine, it’s being used in the sample/development application and I’ve used it to communicate between two Android devices.