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i have a tracking device Meiligao VT310 which send me messeages over gprs. I successfully read messagess with this code but it's not the same as I expected.

private void ReadCallback(IAsyncResult result)
   Client client = result.AsyncState as Client;
   NetworkStream networkStream = client.NetworkStream;
   int read = networkStream.EndRead(result);
   string data = this.Encoding.GetString(client.Buffer, 0, read);

   networkStream.BeginRead(client.Buffer, 0, client.Buffer.Length, ReadCallback, client);

I expect output in NMEA format, but output is like this:

$$\0}E!@ 5/??U154108.000,V,4619.3051,N,01549.5325,E,0.00,0,040112,,*1B|0.0|244|0000|0008,0006|0125004600323C97|0E|0000099C??\r\n

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Sooo what did you expect? looks like GPS coordinates –  Shai Jan 9 '12 at 14:06
Messages contains the unknown characters like \0}E!@ 5/?? and *1B|0.0|244|0000|0008,0006|0125004600323C97|0E|0000099C??\r\n –  PATO7 Jan 9 '12 at 14:17
OK but what did you expect to get? –  Shai Jan 9 '12 at 14:31
something like this $GPRMC,081836,A,3751.65,S,14507.36,E,000.0,360.0,130998,011.3,E*62 –  PATO7 Jan 9 '12 at 15:30
If your getting invalid characters this sounds more of an encoding problem. How is this device connected to the computer in question? –  Ramhound Jan 9 '12 at 15:53

1 Answer 1

up vote 0 down vote accepted

Meiligao VT310 uses its own protocol known as Meiligao GPRS Communication Protocol.

GPRS (TCP/UDP) packet command format are the following:

From server to tracker:


From tracker to server:


It's not NMEA at all but it may uses GPRS NMEA 0183 GPRMC protocol within its data part.

Resources of interest:

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