Hi
I'm novice in Gprs World, so i want make transfert of data between two gprs modem, one is connected to a PC in Serial mode (so posibility to programm with AT commands) and an other is not connected to PC (it contains an embedded application).
So i know the At comnds that makes gprs attach and pdp activation but i've not understand how can i communicate with another modem (with at commnds i mean i've not ip adress of the second modem...).
So if u can help me !
Thanks a lot
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Hi,
Like the ModemXpert mentioned you need the TCP/IP library support your modem. I'm assuming that you have support for that . Pertaining to your question of not knowing the IP address of the other modem, there is one possibility of using some other means like SMS/GSM connection for conveying configuraiton information like IP address, port, etc. Each time any of these parameters change, the modem can convey to the peer. Let me know if this works.
Regards,
The question was:
"i want make transfert of data between two gprs modem"
And should actually read:
"i want to transfer data between two applications, each connected via a gprs modem line. One application runs on a PC with
gprs modem attached via serial port and the other application runs on some embedded device with gprs modem access".
Now the interesting part is what network capabilities your embedded device has? Look for some UDP (or TCP) network sockets, else some other network access.
The PC application should have all possible network capabilities (else install linux :-)
Now you should consider how much data you need to send and how often. This determines type of connection. I would guess that in most cases you just need a UDP connection. Now you need to know the address of your two application network endpoints.
You must comment a bit more in order to get further help.
I have now seen many answers that involves exchanging IP addresses via some protocol (csd dialup, sms, http web site) - very nice but it's most often shaky when the IP address is dynamic. Especially when its a mobile GPRS device where dyn IP can cange very often just when moving around. (GPRS routing area updates). But is doable.
But my point is that there are currently only 2 safe methods for 2 direct communicating GPRS devices: IPv6 static address OR Mobile IP address. In few years IPv6 is standard on wireless devices (you can quote me on that :-) until then look for Mobile IP supported devices.
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by: ModemXpertPosted on 2005-10-04 at 00:36:48ID: 15012073
Hello,
The GPRS link is packet oriented and can not be compared with a circuit switched link (like a standard modem to modem connection).
However, you can make the GPRS link behave like a packet orienter link with streaming serial data transported from one side to the other. In order to do this you must have some kind of data transport protocol above the GPRS bearer.
TCP or UDP can be used, but in order to use those you need support for them in the modem and in the PC.
I do not know if your GPRS modem (or your embedded application) have built-in support for TCP/IP?
If not, you better get another modem...
If it has TCP/IP then its only a matter of AT-command control/monitoring.