GPRS problems !! Dumbfounded and stuck for 2 months !!! :(

[nithinjaganathan]

We are facing a rather unique problem while attempting to continuously (every 2 minute intervals) send data through GPRS with SIM300 modem. When we attempt to send from 1 device to the server, there is absolutely no problem. However, our application requires multiple (40-50 modems) SIM300 modems to communicate to the server (static IP) simultaneously. When we attempt the above, some modems fail to get an IP from the network service provider or lose their GPRS connection. If the GPRS connection is lost, the modem is made to connect all over again. During this re-trying, sometimes, the GPRS connection is successfully made but at other times, it fails (as shown below). Multiple attempts to reconnect still result in failure!!

AT+CSTT="WWW","","" // <APN>,<User Name>,<Password>
OK
AT+CIICR // Bringing up wireless connection via GPRS
OK
AT+CIFSR //Getting an IP for the client 112.79.134.227
AT+CIPSTATUS //Getting the status of the modem
OK
STATE: IP STATUS
AT+CIPSTART="TCP","180.151.50.133","2020" // Opening the Socket
OK
STATE: TCP CONNECTING
CONNECT FAIL


We are unable to find the problem itself as the network service provider claims there is no limitation to the number of devices (only bandwidth limitation; and the data that we send is very minimal, say packet size of 200 bytes). We are unable to debug this problem and are sitting on this for over 2 months with no solution. Any help from your side is greatly appreciated !!!

 

[horace1]

never tried anything on this scale! I have had probelms getting individual modems to connect to the service provider and/or get an IP address but I just keep trying until it works, none of the applications so far being time critial. Often I find it is a problem of signal level, have you tried using AT+CSQ to check the signal quiality?
I asume if you need reliable communications you are using TCP virtual circuits rather then UDP datagrams. Have you thought of using a SOAP over SMS? saves having to get an IP address.