Question

I’m using a TK102 GPS localizer. Along with it, I got only simple end-user docs. No API, dev specs or similar for writing code that will use this localizer.

I was told that it uses UDP. So I wrote a simple PHP listener. But either localizer is not using UDP or something is wrong in communication between it and server. Listener works fine (gets UDP packets from other clients) and localizer is sending something (I’m being charge by GSM operator for GPRS transmission), but the data it sends, doesn’t reach server.

I asked about server or networking issues on Unix/Linux and SuperUser. Here I would only ask, if someone knows any API/dev-specs for this localizer, so I can check, if it really uses UDP or if I haven’t made any other error (in configuration for example).

Answer 1

The localizer and its clones

We’re talking about Xexun TK102 Tracker here. The original one, because there are many clones under other companies from China, selling similar GPS localizer, with the same cover and logo, but with:

• less performance electronics on-board (for example — able to report location once per 20 or 30 seconds, not once per 5 seconds like in original one),

• the ones that are sending lesser information (lack of direction/bearing, altitude, number of satelites used for location fix and many more),

• units using different format of data or non-standard transmission protocol for sending it (for example, cheaper units are unable to use UDP protocol and are transmiting data through TCP protocol, using packets that not always follows standards or definictions.

Coban and Kintech are only two of many clones sold on eBay and in e-shops, claiming to be original Xexun trackers.

On the other hand, original Xexun and some clones (like Coban for example) are harder to control from own script, because they require a correct answer from the server, where data is sent over GPRS. If unit does not receive such reply, it breaks connection. The cheapes unit does not have this checking and will always sent location data to specified IP address over provided port.

Product description

Here is product description of original Xexun localizer (and here is a clone under Kintech name).

Possible buyer must be very careful (and should secure return policy, for which buying directly in China is not recommended) as there are many reports about sellers claiming to sell original Xexun device and sending a clone actually.

Though this device is five years old, it is still sold at many places (including eBay), but even at theses sources it is very hard to get anything worth for developers, except some simple, very basic user guide.

I have confirmed information (from two different sources) that there is no official API available for this device. The only option is to Google around, ask other users or use forums (see below).

If you own original Xexun localizer, you may try to contact company international departament and ask their technicians to include some changes to device source code and to send you updated firmware, with your changes – wow! That was confirmed by company itself.

Forum

I found a perfect forum for TK102 device, with a lot of questions and answers:

• here is a general forum on TK102 device (kept alive for 4,5 year with 171 pages and 2000+ posts!),

• here you’ll find more specific topic on receiving data from this localizer,

• this forum is also about TK102 unit, but it is entirely in French.

There are many other devices dissussed and in general, this is the biggest forum in the world, with topics for localizers and simillar information.

GPRS Protocol Specs

In general, any TK102 related devices is opening a socket for a direct TCP transmission (original one can be switched to use UDP protocol). Data is being transsmited over port specified by user, in configuration and using GPRS only (requires SIM card with enabled GPRS, there is no way to use WiFi).

Sending frequency, format and amount of data being send, entirely depends on kind of device is being used — it is more extensive and more configurable in original one than in clones.

Using FileDropper I shared GPRS Protocol Specification for TK102 Geolocalizer. It contains basic information on how to setup TK102 (and possible all its clones) to send location over GPRS. And what sort of data you should except to receive from in, on server side. This could be useful for someone.

BTW: If links goes dead, contact me for a reupload or sending it over e-mail

Correct server response problem

Make sure, if you’re using correct data transmission protocol! Many (really many) cheap clones uses TCP, while only original TK102 allows switching to UDP. This is convenient, because you need really basic server configuration to handle TCP connections, while you have to use specific server-side software (like node.js) or specific configuration (open to certain ports) to handle UDP. But the key thing is to determine correct protocol, as listening to TCP data, while your localizer sends UDP, will most certainly fail.

Take into consideration, that many TK102 clones requires a correct response from the server after each data, it send. It breaks connection after sending some welcome garbage UDP packet, as it does not receive response, it waits for.

It is quite hard (quite impossible?) to find any guide to many of these clones, on what kind of responses server should sent. This often leads into situation of developer being unable to estabilish two-way communication between server and localizer. Many localizers are sold to be used only via SMS communication or throughs paid services that had signed and agreement with producer and received protocol specification that contains valid responses server should generate for particular TK102 clone.

Double check, if this is not source of problem, if you can’t communiacte with your localizer from your app.