Advise on BLE

Im building an android app for a BLE device. It is suposeed I need to send HEX commands to the device and the device return a result. Im following this tutorial: [login to view URL] I can connect to device but not capabale to send or receive commands. Im suspicious that the hex is send in text... but not sure. I need you to help me send a command and receive the result on apk Because is advisory service, the task is done trought Teamviewer Device manufacturer provided this information: 2、0x71 Function : Get Time Send : 0x71 00 00 00 00 00 00 00 00 00 00 00 00 00 00 CRC Parameter : N/A Return : 0x71 AA 00 00 BB CC DD EE 00 00 00 00 00 00 00 CRC AA=0x01 : The command completed successfully AA=0x00 : Command execution failure or CRC check errors BB CC DD EE is Little-endian format time , The unit is in seconds , It is a relative time , Benchmark for at 0:00:00 on January 1, 2000 . For example : BB CC DD EE as 92 F3 74 1D ,then the time is 0x1d74f392=494203794 seconds , So“0:00:00 on January 1, 2000 ”+ “494203794”= “22:49:54 on August 29th, 2015”