Question about delegate(IOBluetooth)

[Realbuber]

sorry I am a begineer here,

  @objc.typedSelector(b"v@:@^vQ")
  def rfcommChannelData_data_length_(self, channel, data, length):
      print(f"DATA::{data}")
  
  @objc.typedSelector(b'v@:@@I')
  def rfcommChannelWriteComplete_refcon_status_(self, rfcommChannel, refcon, status):
      if status == 0:  # kIOReturnSuccess
          print("Data sent successfully.")
      else:
          print("Failed to send data.")

I've tried a lot of way, rfcomm channel can connect and open successfully, also I can send the data to my device and get the call back in delegate method(rfcommChannelWriteComplete_refcon_status_), but the read data always failed, I don't know how to trigger the rfcommChannelData_data_length_ method, am I miss something?