private boolean checkFirstByte(byte first){
  return (first == (byte)0x02) || (first == (byte)0x81) || (first == (byte)0x01)|| (first == (byte)0xC1)|| (first == (byte)0x03)|| (first == (byte)0x13);
}

private boolean checkFirstByte ( byte first ) { return ( first == ( byte ) 0x02 ) || ( first == ( byte ) 0x81 ) || ( first == ( byte ) 0x01 ) || ( first == ( byte ) 0xC1 ) || ( first == ( byte ) 0x03 ) || ( first == ( byte ) 0x13 ) ; }
this function checks that the first byte of the received message is correct .
