JT/T 808-2019[Including 2021XG] GNSS for operating vehicles - General specifications for vehicle terminal communication protocol and data format (English PDF)

3.1 Terms and definitions

The following terms and definitions apply to this document.

3.1.1

Abnormal data communication link

The state in which the wireless communication link is disconnected, or temporarily suspended (such as during a call).

3.1.2

Register

An operation that the terminal sends a message to the platform, informing that it is installed on a certain vehicle.

3.1.3

Unregister

An operation that the terminal sends a message to the platform to inform the removal from the installed vehicle.

3.1.4

Authentication

When the terminal is connected to the platform, it sends a message to the platform to verify its identity, at the same time reports the version of the protocol currently used to communicate with the platform.

3.1.5

Location reporting strategy

Rules for timed, distanced reporting or a combination of both.

3.1.6

Location reporting program

The rules for determining the location reporting interval, according to the location reporting strategy.

4.1 Communication method

The communication method, which is adopted by the protocol, shall comply with the relevant requirements in JT/T 794.The communication protocol shall adopt TCP or

UDP, the supervision/monitoring platform (hereinafter referred to as the "platform") shall serve as the server end, whilst the on-board terminal of the road transport's vehicle satellite positioning system (hereinafter referred to as "the terminal") serves as the client.

When the data communication link is abnormal, the terminal can use SMS messages to communicate.

4.2 Data types

The data types, which are used in protocol messages, are as shown in Table l.

4.3 Transmission rules

The protocol shall communicate words and doublewords in big-endian network byte order. The transmission rules are agreed as follows.

4.4 Composition of messages

4.4.1 Message structure

Each message is composed of identification bit, message header, message body, check code. The message structure is as shown in Figure 1.

Identification bit Message header Message body Check code Identification bit

4.4.2 Identification bit

The identification bit shall be represented by 0x7e. If 0x7e and 0x7d appear in the check code, message header, message body, escape processing is required. The escaping rules are defined as follows.

4.4.3 Message header

4.4.3.1 See Table 2 for the content of the message header.

4.4.3.2 The message body's attribute format structure is as shown in Figure 2.

4.4.4 Message body

The format and content of each different command message body is determined by each command, see Chapter 7 for specific requirements.

4.4.5 Check code

The calculation rule of the check code shall start from the first byte of the message header, XOR operation with the next byte, until the end of the last byte of the message body; the length of the check code is one byte.

5.1 Connection establishment

The daily data connection -- between the terminal and the platform -- can use TCP or

UDP. After the terminal is reset, it shall establish a connection with the platform. After the connection is established, it will immediately send a terminal authentication message to the platform, for authentication.

5.2 Maintenance of connection

After the connection is established and the terminal authentication is successful, the terminal shall periodically send a terminal heartbeat message to the platform; the platform will send a platform general response message to the terminal, after receiving it; the sending period is specified by the terminal parameters.

5.3 Disconnection of connection

Both the platform and the terminal shall actively determine whether the connection is disconnected.

The platform shall use the following methods, to determine whether the terminal connection is disconnected.

6.1 TCP and UDP message processing

6.1.1 Messages mainly sent by the platform

All messages sent by the platform shall require the terminal to respond. Response is divided into two ways.

6.1.2 Messages mainly sent by the terminal

6.1.2.1 Normal data communication link

When the data communication link is normal, all messages mainly sent by the terminal shall require the platform to respond. Responses shall be divided into general responses and specific responses, which are determined by specific functional protocols. After the terminal waits for the response timeout, it shall resend the message.

6.1.2.2 Abnormal data communication link

When the data communication link is abnormal, the terminal shall save the location information report message to be sent. The saved message shall be sent, as soon as the data communication link is restored.

6.2 SMS message processing

When the terminal communication mode is switched to the SMS message mode, the

PDU eight-bit encoding method shall be adopted. For messages with a length exceeding

140 bytes, sub-packaging processing shall be carried out, according to the SMS service plan.

7.1 Classification

Protocols are described in functional categories. If not specified, the TCP communication mode is used by default. See Appendix A, for the communication protocol between the onboard terminal and the external device. See Appendix B, for the message comparison between message names and message IDs in the protocol.

7.2 Terminal management protocol

7.2.1 Terminal registration/deregistration

When the terminal is in the unregistered state, it shall register first. After the registration is successful, the terminal obtains the authentication code and saves it. The authentication code can be used, when the terminal is authenticated. Before the vehicle removes or replaces the terminal, the terminal shall perform a logout operation, to cancel the corresponding relationship between the terminal and the vehicle.

7.2.2 Terminal authentication

Registered terminals shall be authenticated, immediately after establishing a connection with the platform. The terminal shall not send other messages, before the authentication is successful.

7.2.3 Set/query of terminal parameters

The platform sets terminal parameters, by sending a terminal parameter setting message;

the terminal replies with a general terminal response message. The platform inquires terminal parameters, by sending an inquiry terminal parameter message; the terminal replies with an inquiry terminal parameter response message.

7.2.4 Terminal control

The platform controls the terminal, by sending a terminal control message; the terminal replies with a general terminal response message.

7.3 Position and alarm protocol

7.3.1 Position information report

The terminal periodically sends location information report messages, according to parameter settings.

According to the parameter control, the terminal can send a position information report message, when it judges that the vehicle is turning.

7.3.2 Location information query

The platform queries the current location information of the specified vehicle terminal, by sending a location information query message; the terminal replies with a location information query response message.

7.4 Information protocol

7.4.1 Sending text information

The platform sends a message, by sending a text message; notifies the driver, according to the specified method. The terminal replies with a general terminal response message.

7.5 Telephony protocol

7.5.1 Callback

The platform requires the terminal to call back the phone, according to the specified phone number, by sending a call back message; specify whether to follow the monitoring mode. When calling back, the terminal shall not turn on the loudspeaker.

The callback message requires the terminal to reply with a general terminal response message.

7.6 Vehicle control protocol

The platform requires the terminal to control the vehicle, according to the specified operation, by sending the vehicle control message. After receiving it, the terminal shall immediately reply with a general terminal response message. After replying to the general response message, the terminal shall control the vehicle; then reply the vehicle control response message, according to the result.

7.10 General data transmission category

Messages, that are not defined in the protocol but need to be transmitted in actual use, can use data uplink transparent transmission messages and data downlink transparent transmission messages, for uplink and downlink data exchange.

7.11 Encryption protocol

If encrypted communication is required between the platform and the terminal, the RSA public key cryptosystem can be used. The platform informs the terminal of its own RSA public key, by sending the platform RSA public key message; the terminal replies with the terminal RSA public key message, and vice versa.

8.1 Terminal's general response

Message ID. 0x0001.

The data format of the general response message body of the terminal is as shown in

Table 4.

8.2 Platform's general response

Message ID. 0x8001.

8.3 Terminal heartbeat

Message ID. 0x0002.

8.4 Query server time request

Message ID. 0x0004.

The terminal sends a request to the server, to query the server time; the message body is empty.

8.5 Query server time response

Message ID. 0x8004.

The server responds to the query server request, which is initiated by the terminal.

The data format of the query server time response message body is as shown in Table 6.

8.6 Subpackage retransmission request of sever

Message ID. 0x8003.

See Table 7, for the data format of the message body of the subpackage retransmission request.

8.7 Subpackage retransmission request of terminal

Message ID. 0x0005.

8.8 Terminal registration

Message ID. 0x0100.

The data format of the terminal registration message body is as shown in Table 8.

8.9 Terminal registration response

Message ID. 0x8100.

The data format of the terminal registration response message body is as shown in Table 9.

8.21.2 See Table 26, for the format of additional location information items.

8.23 Location information query response

Message ID. 0x020l.

8.24 Temporary position tracking control

Message ID. 0x8202.

See Table 34, for the data format of the temporary location tracking control message body.

8.25 Manual confirmation alarm message

Message ID. 0x8203.

The data format of the manual confirmation alarm message body is as shown in Table 35.

8.26 Link detection

Message ID. 0x8204.

The message body is empty.

8.27 Issuing text messages

Message ID. 0x8300.

See Table 37, for the data format of text information issuing message body.

8.28 Callback

Message ID. 0x8400.

The data format of the callback message body is as shown in Table 39.

8.29 Setting phonebook

Message ID. 0x840l.

Set the message body data format of the phonebook, as shown in Table 40.

8.30 Vehicle control

Message ID. 0x8500.

The data format of the vehicle control message body is as shown in Table 42.

8.31 Vehicle control response

Message ID. 0x0500.

See Table 44, for the data format of vehicle control response message body.

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