Android Bluethoot socket connection - sockets

Question

hello I connect my device android to printers, of the way follows.
bluetoothAdapter = BluetoothAdapter.getDefaultAdapter();
BluetoothDevice bluetakebt220 =
bluetoothAdapter.getRemoteDevice(obj.getMac().toString());
BluetoothSocket mBTsocket= null;
bluetoothAdapter.cancelDiscovery();
UUID num = UUID.fromString("00001101-0000-1000-8000-00805F9B34FB");
mBTsocket = bluetakebt220.createRfcommSocketToServiceRecord(num);
mBTsocket.connect();
this works well for for most devices, but some do not connected, ¿that can be due?

Answer 1

The most obvious reason I can think of is the UUID's do not match up. If you are making a generic app you need to have the UUID of each printer. This can be done in the form of a case switch statement.
Code
switch(Mac Address) {
case (Mac Address 1)
UUID = xxxxxxxx-xxxx-Mxxx-Nxxx-xxxxxxxxxxxx
case (Mac Address 2):
UUID = xxxxxxxx-xxxx-Mxxx-Nxxx-xxxxxxxxxxxx
default:
UUID = 00001101-0000-1000-8000-00805F9B34FB;
The reason why most of the time your connections works is because 00001101-0000-1000-8000-00805F9B34FB is the generic ID for most off shelf hardware devices (keyboards,mouses,printers,scanners etc). The minute your UUID does not match a connection cannot occur. Read this for more info about UUID's.

Answer 2

the device acts equal, simply does not establish proper connection , but yes allow write in
Here is the code if someone can help
UUID num = UUID.fromString("00001101-0000-1000-8000-00805F9B34FB");
bluetoothAdapter = BluetoothAdapter.getDefaultAdapter();
BluetoothDevice bluetakebt220 = bluetoothAdapter.getRemoteDevice(obj.getMac().toString());//PRINTER ADAPTER FOR LPT BLUETAKE BT220
BluetoothSocket mBTsocket= null;
mBTsocket = bluetakebt220.createRfcommSocketToServiceRecord(num);
bluetoothAdapter.cancelDiscovery();
mBTsocket.connect();
OutputStream os = **mBTsocket**.getOutputStream();
os.flush();
byte[] CPCLFormat = null;
PCLFormat = objImpresion.getTexto().getBytes("utf-8");
os.write(CPCLFormat);//se imprime el texto
os.flush();
os.close();
.I simply comment msocket.isConnected and write directly after open connection. i don´t why happen