I have been tasked with writing a C# / WPF app that displays location information of vehicle GPS tracking devices out in the field, which use a GPRS modem for communications. The tracking device in question is a Meitrack device (http://www.meitrack.net/). This device can send and receive data via GPRS and SMS.
Looking at the protocol, the device can transmit data to the server using this message structure:
@@<Data identifier><Data length>,<IMEI>,<Command type>,<Command><* Check code>\r\n
And the server can transmit data to the device using this structure:
$$<Data identifier><Data length>,<IMEI>,<Command type>,<Command><* Check code>\r\n
Now I'm unfortunately not very clued up with GRPS communications. My first question is, do I need a GPRS modem on the server side for all of this to work? Or can the tracking units transmit GPRS data to a specific IP address using TCP or UDP, where the server (with a static IP address) would be listening? If the latter is the case, it would be sufficient for the server to simply have an internet connection, and would not require a GPRS modem?
However, looking at the protocol, I see a parameter called IMEI. This I know is a unique identifier for all cellular devices. So it looks as if that is the method of communications for this tracking device? I.e. All comms stays in the cellular network (and does not enter the internet) and communicates with other devices by addressing their IMEI? In this case the server WOULD require a GPRS modem.
So my first question is if a GPRS modem will be required on the server side or not. Or can I get away with the server simply having an internet connection, and using IP addresses instead of IMEI or SIM numbers? And if that is the case, would each tracking device also require a static IP address if the server wished to talk back to the tracking device?
Sorry for my ignorance. I've used GSM modems many years ago for sending and receiving SMSes via AT commands, but I've never used them for GPRS data.
Thanks in advance for any support...
Without knowing this particular product, this is how I understand it works:
The GPRS modem forms a mobile connection to your mobile operator's network. On top of this mobile connection, it needs to form an IP connection to a server in the operator's network. Via this server (access point), you can access the internet, including your own server, just as you would via any internet service provider.
Your server only needs a normal internet connection.
The IMEI in the above messages seems to be just an identifier for the tracking device - it's not actually needed for the connection. The mobile network takes care of routing IP packets to the correct GPRS device.
The tracker is just like any computer accessing the internet via a service provider - it can download and upload information.
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