I am developing an app which will have multiple phones communicating together concurrently via bluetooth. To this end, I extended the BluetoothChat example to support multiple simultaneous connections. Once I got it working with 3 phones, I ramped up to 4 but have discovered that it appears that phones running Android 2.2 can only support 2 simultaneous bluetooth connections, while phones running 2.3.4 can support 3 (at least, if not more). Can anyone confirm this as a known bug for 2.2? It would be good to know if this is just a hard limitation.
Phones I am testing with: HTC Incredible (2.2) Nexus S (2.3.4) Nexus 1 (2.3.4) Nexus 1 (2.3.4) Here's how I determined that there is this hard limit: My code extends the BluetoothChat sample program, as I said. Unfortunately I cannot share it right now (company legal limitations) but it's basically the same as the original except that all threads are not killed when new connections are made, all ConnectThread and ConnectedThread objects are stored in an array, and I kick off a new AcceptThread whenever an incoming connection is turned into a ConnectedThread. After instrumenting my code with lots of debug, what I've found is that once my 2.2 device (the incredible) has established 2 connections, it will literally hang at either the accept() in the AcceptThread or at the connect() in the ConnectThread. This is true with whichever order of connections are made. For example, if I do the following: 1. Incredible > NS 2. Incredible > N1 (1) 3. Incredible > N1 (2) or 1. Incredible > N1 (1) 2. Incredible > N1 (2) 3. Incredible > NS or 1. Incredible > N1 (either) 2. Incredible > NS 3. Incredible > N1 (either) or 1. NS > Incredible 2. N1 (either) > Incredible 3. N1 (either) > Incredible In all cases, the Incredible will Always hang on step 3, whether it's on the connect() in the first 3 cases, or the accept() in the last case. Debug shows that it hangs specifically on those calls (not the RFComm socket creation calls or anything else). Now, there are other potential connection orders but these are the basic ones that need to work, so I'm not worried about interleaving connects and accepts right now. The other interesting thing is that I instrumented an end program method from the menu which calls cancel on all open threads. According to the SDK, when you call close() on an open hanging socket, it is supposed to throw an error. Well, if the app has already hung on either accept() or connect() in any of the scenarios above, then the close() call hangs as well and I have to forceclose the program. Other info: - Using another N1 running 2.3.4, I found that I didn't have any trouble connecting all 4 phones as long as the incredible wasn't in the mix. - Also, when a phone running 2.3.4 with 2 active connections tries to connect to the incredible while the incredible has 2 other active connections, the phone running 2.3.4 fails to connect and does not hang, while attempting the connection in reverse has the (now) expected hang. - Also tried to connect 4 phones with a Samsung Infuse (2.2) and another N1 running 2.2. Both cases had similar hangs (cannot exhaustively check this thanks to limited access to the devices). - When trying to establish a 3rd connection with a device which is not there (turned off the bluetooth on one of the N1s), the connect() call does NOT hang. However, if I then turn on BT on the 3rd phone and try to reconnect, it's back to hanging at connect(). Therefore there definitely appears to be some kind of connection management problem when running 2.2. - If I make 2 connections on the incredible, then close one, I can open another. All closing/opening works fine as long as I'm only trying to manage 2 connections. Anyways, as I said, if anyone can confirm that I simply cannot use my 2.2. device for testing more than 2 concurrent connections, that would be very helpful. -- You received this message because you are subscribed to the Google Groups "Android Developers" group. To post to this group, send email to [email protected] To unsubscribe from this group, send email to [email protected] For more options, visit this group at http://groups.google.com/group/android-developers?hl=en
