BlackKite, Vehicle Tracking System User Manual
Rev. 1.4.0
Zilogic Systems
Page 43
9.3. MAIN Message
The MAIN message is sent by the device to the server periodically. The periodicity is configurable.
Location, Status and Timestamp tags are available in the MAIN message. In addition, other vehicle
information can also be added through the device configuration. Please refer Vehicle Information
for additional available tags.
If the ACK message for the MAIN message is not received, within a timeout period, the data will be
stored in the archive, and will be re-transmitted at a later point of time.
Within a packet, the tags are organized in increasing order of tag type. When messages are trans-
mitted from the archive, the main pack can contain several records from the archive. The structure
of an aggregate packet is shown in the following diagram.
Figure 9.1. Packet Structure
The receiver can use the fact that the tags within the record are ordered, to determine the start
of a new record.
9.4. ALERT Message
ALERT messages are sent after a change in vehicle parameters. Refer Section 4.5, “Alerts” for the
list of available alerts. The content (the tags) of the ALERT message is same as the MAIN message.
If the ACK message for the ALERT message is not received, within a timeout period, the data will
be stored in the archive, and will be re-transmitted at a later point of time.
9.5. Vehicle Information
The vehicle information sent as part of HEAD, MAIN and ALERT messages is organized as pairs of
tag types and tag values. The tag type indicates the content and the format of the tag value. The
currently supported tag types and the format of the tag values is listed below.
IMEI
• Tag Type:
0x03
• Length: 15 bytes
• Format: ASCII characters
• Example: The IMEI number 357804043399918 is represented in ASCII format in the packet
as
33 35 37 38 30 34 30 34 33 33 39 39 39 31 38
Java Code to Compute IMEI.
import java.io.UnsupportedEncodingException;
public class BlackKite {
/*
