HM-10 Bluetooth: How to read characteristic data via serial commands
Assuming you send AT commands via UART to the HM-10 module it's programmed not to receive them while it's connected by default. This is described in the datasheet http://www.jnhuamao.cn/bluetooth40_en.zip  


  Mode 0: 
  
  
  Before establishing a connection, you can use the AT command configuration module through UART. 
  After established a connection, you can send data to remote side from each other.
  


If you send an AT command in Mode 0 you will make the module disconnect and then it's gonna be ready to receive AT commands. You can program it to not do this and receive them but not execute them until you send a command to do so.

The datasheet also describes mode 1 and mode 2 where you can also send AT commands over bluetooth from the connected device and it will not disconnect.


  Mode 1:
  
  
  Before establishing a connection, you can use the AT command configuration
  module through UART.
  After established a connection, you can send data to remote side. Remote side
  can do fellows:
  
  
  Send AT command configuration module.
  
  ... more cool stuff