OK+SEND: TX_LEN means the data sending request is successful,
TX_LEN: 1Byte, the length of the sent data
OK+SENT: TX_CNT means the data is sent successfully, TX_CNT:
1Byte, the number of times the data is sent.
ERR+SEND:ERR_NUM indicates that the data sending request failed,
and the reason is indicated by ERR_NUM. ERR_NUM: 1Byte,
0- not connected to the network
1- Communication is busy, sending request failed
2- The data length exceeds the current sendable length, only send the
MAC command
ERR+SENT: TX_CNT means that the data transmission failed, and the
number of transmissions reached the maximum number, TX_CNT:
1Byte, the number of data transmissions.
OK+RECV: TYPE, PORT, LEN, DATA data received successfully
(received response message or active downlink data)
TYPE: 1Byte, downlink transmission type
Bit0 : 0-unconfirm, 1-confirm
Bit1: 0-not ACK, 1-ACK
Bit2: 0-not carried, 1-carried, indicating whether the LINK command
response is carried in the downlink data
Bit3: 0-not carried, 1-carried, indicating whether the TIME command
response is carried in the downlink data, only when the bit is 1, it means
that the time synchronization is successful
Bit4~Bit7: Default 0, reserved
PORT: 1Byte, downlink transmission port
LEN: 1Byte, downlink data length
DATA: nByte, downlink data, when LEN=0, this field does not exist.