RS232 over GPRS request

[bogdantk]

Hello,
I need to read a series of energy meters, distributed over a large area. The meters have a RS232C serial interface a a very simple ASCII protocol to read current registers and set-up the meter (real time clock/calendar). Until now the reading was done once a day with a laptop (the meter has a history register related with the RTC). We want to introduce a GSM modem connected in a GPRS network. In the network there is a VPN and therefore we can have fixed IP's for the emote locations. My problem is:  I know the script to connect the modem to the network, but how to read the data from the meter. In normal GSM modem (dial up ) the modem is in transparent mode so after dialing and connecting the RS232 is transparent and the meter can be read but the mode is to slow. How can I send/read information from the RS232 line after the modem is connected (has it's own IP) in the GPRS network ? Please advise.
Thank you.
I searched the forum but I found no relevant  information.

[DreamCat]

are you sure it is RS232 interface of energy meters that you used?  in our country, it must be RS485.
I just done a device (CDMA + energy meter), but only two way: TCP/IP and SMS, I didn't try to implement VPN on it.  could you like share some document to me about vpn on GPRS?

I use a double UART microcontroller, connected to RS485 interface and a cdma module; in addition I use software simulate a uart to do some config for my device.
so I only need send broadcast command to those energy meters intervals 30 minutes, and open the tcpip link to send the data received from meters.

yeah,  the baudrate of energy meter's interface is very slow. it for environmental interference to correct transmission of data.

or you can change the energy meter's baudrate to higher, but, it is also slow....

but you really need read meter real time? I think this is unnecessary.