BT Socket Factory creation and connecting with java code

[Aniket392]

• Add C4BTSocketFactory, registers C4SocketFactory with LiteCore and handles all JNI callbacks (open, write, close, requestClose, dispose, attached)
• Add LiteCoreBTSocket, bridges BluetoothSocket L2CAP channel with LiteCore's C4Socket; implements SocketFromCore with read loop, write queue, and flow control
• Add NativeC4BTSocketFactory, JNI implementation for nRegisterFactory and nFromNative

[pasin]

Related PR : https://github.com/couchbaselabs/couchbase-lite-java-ee-root/pull/390

[pasin]

There are lot of detail and setup in this PR, and I think we will need to setup an person review.

However, I have looked up where we put the current WebSocketFactory and CBLWebSocket classes. I think we should move LiteCoreBTSocket and C4BTSocketFactory to the EE repo under android's com.couchbase.lite.internal.. We may need to rename it without C4 and Core prefix (e.g. BluetoothSocketFactory and BluetoothSocket : Use the names that are consistent with others).

As a reference, where CBLWebSocket / SocketFactory are :

https://github.com/couchbase/couchbase-lite-java-common/blob/b7bcaf74dd4f4752ba75e05f5adaaf6988931df6/android/main/java/com/couchbase/lite/internal/replicator/CBLWebSocket.java

https://github.com/couchbaselabs/couchbase-lite-java-ee-root/blob/master/ee/common/main/java/com/couchbase/lite/internal/SocketFactory.java

[pasin]

Based on https://developer.android.com/ndk/guides/jni-tips, it's a good practice to call ExceptionCheck() and ExceptionClear() to handle both caught and runtime exception when calling Java code such as

if (env->ExceptionCheck()) {
        env->ExceptionDescribe(); // Log to logcat or stderr
        env->ExceptionClear();
    }

You may check if we have don't this anywhere else or have any helper function for this. If not, I suggest to create a helper function to do this or create a ticket to take care this later if the method doesn't declare throws.

[Aniket392]

Currently in code base i can't see similar checks
I will create ticket for same

[pasin]

This will cause the default c4socket factory to be a Bluetooth factory and I don't think we would want that. The correct way to return the socket factory for bluetooth is via C4PeerDiscoveryProvider's getSocketFactory() function.

[Aniket392]

So what i can understand is, we can override the getSocketFactory in c4PeerDiscovery.hh in BluetoothProvider
and then we don't need to register it, right?

[pasin]

That is right. We don't need to register.

[pasin]

The socket needs to be wrapped with TLS enabled socket to get the TLS encryption. This is what is done in iOS but currently c4SocketFromNativeWithTLS () is in the TLSCodec.hh, and the header is not included in the package as a public header.

Ref<C4Socket> C4PeerDiscoveryProvider::createIncomingSocketWithTLS(C4SocketFactory const& factory,
                                                                   void* nativeHandle,
                                                                   C4Address const& address)
{
    return net::c4SocketFromNativeWithTLS(factory, nativeHandle, address, _discovery.tlsContext().get());
}