Communication Between Two GSM(SIM-508) module

As Per says, the trouble with the dynamic IP addresses allocated by GPRS opertors is not just that they are dynamic, but also that they are (usually) "private" - ie, they are effectively "hidden" behind a firewall and not visible outside the particular GPRS network.

In fact, I don't think that there is even any guarantee that devices on the same GPRS network will be able to "see" each other's IP addresses.

You might be lucky, and it might just happen to work if, for example, your two devices are in the same cell - but don't count on it!

There are specialist service providers who offer solutions to this (like a VPN) - at a price, of course.

As per says, without using any specialist services, the easiest way is to have both units communicate via a common intermediary.

If (and it's a big "if") you can get a sufficient guarantee from your service provider that your devices will always be able to see each other's (private and/or dynamic) IP addresses, then you could have them notify their addresses to each other by SMS od data call...

Again, none of this has anything at all to do with Keil!

As Per says, the trouble with the dynamic IP addresses allocated by GPRS opertors is not just that they are dynamic, but also that they are (usually) "private" - ie, they are effectively "hidden" behind a firewall and not visible outside the particular GPRS network.

In fact, I don't think that there is even any guarantee that devices on the same GPRS network will be able to "see" each other's IP addresses.

You might be lucky, and it might just happen to work if, for example, your two devices are in the same cell - but don't count on it!

There are specialist service providers who offer solutions to this (like a VPN) - at a price, of course.

As per says, without using any specialist services, the easiest way is to have both units communicate via a common intermediary.

If (and it's a big "if") you can get a sufficient guarantee from your service provider that your devices will always be able to see each other's (private and/or dynamic) IP addresses, then you could have them notify their addresses to each other by SMS od data call...

Again, none of this has anything at all to do with Keil!

Thanks for your comment,
Actually i am using Keil, in programming the 8051 for all these task all together, attached with each GPRS module.But unable to find out how to solve this dynamic IP problem.

But as of now, it's clear that i have to communicate via static IP to each other or VPN or on the pity-of-service provider.

Thanks to all of u gr8 minds.

Regards.

Mohit
Bitadvance,
Pune

"i am using Keil, in programming the 8051 for all these task all together"

But the problem is general to any IP network - it has nothing specifically to do with the 8051, or Keil - or even GPRS!

Perhaps you should forget about the 8051, Keil, and GPRS for a moment, and think about how you'd get two PCs to communicate from different LANs...

"it's clear that i have to communicate via static IP to each other or VPN"

You still have the option of going via an intermediate server - possibly your own PC.

Even if the IP address is static, it may still not be public - and you still have the issue of how you will get each unit to know the other's IP address...

Sir,can you plz seuugest me some forum or web-link which related to AT commands query.

Mohit
Bitadvance
Pune

But it's nothing to do with AT commands, is it?

As I said, the issues of IP addressing apply to any IP network!

What you need to understand is IP networking!

eg, try: compnetworking.about.com/.../bldef_tcpip.htm