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How to create an Android RFCOMM socket without any input from the user?

Posted by: admin February 23, 2018 Leave a comment

Questions:

Here’s the scenario:

I need to write an application for Android to create a RFCOMM socket to a PC with a Bluetooth dongle (I’m going to write the server too).

My requirement is that the user doesn’t have to pair device manually.

Actually, with a big hack, I’m using the createInsecureRfcommSocket.

A little scenario: I’ve an Android application which exchanges information with a Linux box with a RFCOMM socket opened. I can manually set the PIN on the devices (hard coding it IS an option)

I’m looking for different roads:

Write a JNI wrapper

As has been done here by Max Kellermann, I can write a JNI layer to make all the pairing phase. This should be a good option, but there’s a problem:

The NDK 4b does not provide libbluetooth libraries, so -lbluetooth fails, as well as the NDK v.3.

Options:

  1. Find the NDK 1.5 (which includes lib bluetooth). After days of web search I’ve been not able to find out. Anyone has or knows where I can find it?
  2. Compile libbluetooth for Android by myself and use them for -lbluetooth. No lucky there, I’m not able to build them. Any hint?

Use something exposed by the APIs

Any one know how can I use createRfcommSocketToServiceRecord and have the user not to manually pair the device? Is it possible? How should I write the server?

Something I do not know

Maybe (sure!) there is something I do not know. Maybe I can use something else? Not RFCOMM? SDP?

Maybe I can manually pair with the Android API?

I hope to have been clear enough, if not just ask. And again, as it’s not the first time, I’m in your hands 🙂

Thanks for all the support guys!

Answers:

At the end, I can say that you can’t.

Even if you find a way, using wrappers, writing C modules and so on, android evolution will probably change the thing you’re using.

And so, there’s no option. Sadly.

Let’s see how Android Bluetooth API will change in the future.

Questions:
Answers:

The Android Bluetooth API is not finalized, and will change. Use at your own risk. This class implements an API to the Bluetooth RFCOMM layer. An RFCOMM socket is similar to a normal socket in that it takes an address and a port number. The difference is of course that the address is a Bluetooth-device address, and the port number is an RFCOMM channel. The API allows for the establishment of listening sockets via methods bind, listen, and accept, as well as for the making of outgoing connections with connect, connectAsync, and waitForAsyncConnect. After constructing a socket, you need to create it and then destroy it when you are done using it. Both create and accept return a FileDescriptor for the actual data. Alternatively, you may call getInputStream and getOutputStream to retrieve the respective streams without going through the FileDescriptor.