FMC packets sending behavior and server response requirements

TELEMATICS
1

Hello,

We have a server receiving data from FMC130, FMC150, FMC650 and FMC920. We handle Codec 8 and Codec 12 (FMC650 only) packets (TCP, with AVL response).

I’m doing improvements of our server, and I would need to better understand how the Codec 8 and Codec 12 data are sent by the devices, and the requirements for the server responses to these packets.

  • Do the FMC devices send the next packet (Codec 8 or Codec 12) only after the response to the previous one is received (or timeout), or can packets and responses be interleaved ?

  • If the packets can be interleaved, are there specific requirements for responses, e.g. response in a separate packet, or a given delay between responses ?

I carefully checked but couldn’t find the answers to this questions in your wiki (in particular Help with Server FAQ - Teltonika Telematics Wiki and Teltonika Data Sending Protocols - Teltonika Telematics Wiki)

Thanks in advance for your reply

2

Hi,

Good day.

Thank you for your detailed questions regarding the handling of Codec 8 and Codec 12 packets from FMC devices.

Here is the clarification:

  • Sequential Packet Transmission: Teltonika FMC devices (FMC130, FMC150, FMC650, FMC920) send Codec 8 and Codec 12 packets in a sequential manner. The device sends the next packet only after receiving a response from the server or after a timeout.

  • No Packet Interleaving: The devices do not interleave packets and responses. Codec 8 and Codec 12 packets are processed one at a time on the same TCP connection.

  • Server Response Requirements:

    • For Codec 8, the server must respond with a 4-byte acknowledgment indicating the number of AVL records received.
    • For Codec 12, the server must respond with a properly formatted Codec 12 response packet, including the correct Codec ID, command type, payload, and CRC16 checksum.
    • Responses must be sent on the same TCP session and preferably within 3–5 seconds to maintain communication stability.

For detailed Codec 12 protocol information, please refer to the official Teltonika wiki:
:link: Teltonika Codec 12 Specification

Kind regards,
Amalnath