Modem to modem data transfer with 2G/3G?


#1

Guys

I need to perform the operation in the pic below with data transmission from supreme 20 to supreme 20. I cannot perform the operation with only one supreme 20 to PC, because certain IP issues and time constraint. :cry:

My networking knowledge is just beginner level. I flipped through the OpenAT Lua tutorials and it seems like all of the examples concern with setting up one modem with a web page. Probably i missed something? :blush:

From my very limited wavecom modem and LUA knowledge, it seems like the data sender supreme 20 need to know the phone number of the data receiver supreme 20 in order to send data over to it with 2G/3G? After the receiver supreme 20 received the data, the PC software sorta need to retrieve the data from the supreme 20 receiver modem in ascii form? :mrgreen:

I beg for any code example or link to code example. :blush:

Thanks, guys.


#2

The “only” thing Open AT Lua gives you is that it lets you write your applications much faster, and that those applications are likely to be way more reliable than if written in C. It eases the programming but won’t do it for you :slight_smile:

Now, if you want to communicate from modem to modem, the obvious way is to get a data plan from your carrier, so that each has an IP address. From there, exchanging data between CPUs connected to the IP network is easy, as long as both IP addresses can see each other (that’s something you want to check with your carrier: you want either one of them to have a public address, or both of them to be in the same private network. All carriers can do that for you, but some will charge extra bucks).

It is possible to send data point-to-point between both modems over GSM, without IP networking, but it will require more system programming, and your bandwidth will be limited. GPRS has to be used with IP by design, as far as I know [EDIT: no, it just needs a paket oriented protocol, as explained by awneil below. Yet for all practical purposes, “normal” users don’t want to think of GPRS without IP].

As for the tutorial: it focuses on the dynamic HTTP server because it’s an easy to understand, visual, pleasant application to fiddle with, and the archetype of what you really don’t want to do in C. And it serves pages over all open IP bearers, not only PPP. Again, the tutorial focuses on PPP bearer because it’s the easiest one to use for development, but it works exactly the same over GPRS. However, dynamic programming is by no way limited to web pages.


#3

Why are you starting a new thread when you already have one on exactly the same problem:
viewtopic.php?f=53&t=1917&p=7213#p7213

It’s a bit rude to, apparently, just discard all the advice you received there without so much as a mention!

What “IP issues”? How do you think that using two modems will resolve them?

Similarly, what “time constraints”? And how do you think that using two modems - with two radio links - will resolve them?

That, unfortunately, is a foundation that you need to lay!

Whether you use Lua, ‘C’, or whatever else, you still need to understand the networking concepts!
You cannot skimp on that!

This has nothing specifically to do with Wavecom or Lua!

Of course, with any communication link, the initiating party needs to know how to contact the receiving party - whether that’s with a phone number, an IP address, a URL, or whatever!

Once the data link is established, the modem can effectively be transparent - the data just flows from the “logger” at the Windsensor to the PC.

Whether you choose to transfer the data in ACII form or something else is entirely up to you!


#4

Not exactly: GPRS is the General Packet Radio Service - the definition covers other packet types besides just IP; eg, X.25.

However, I don’t know that Wavecom support anything other than IP, and most generally-available GPRS subscriptions are just IP (anyone who wanted X.25 would know about it, and ask specifically).


#5

Thanks for the advice guys, and sorry for the rude things i did. :blush:

And I swear I am studying basic GPRS networking stuff now in Tech republic: :blush:
http://whitepapers.techrepublic.com.com/thankyou.aspx?&promo=110000&docid=7414&view=7414


#6

Excellent!

But I think you also need to study some basics of data communications, and TCP/IP networking.

Here’s a TCP/IP tutorial:
compnetworking.about.com/cs/basi … _tcpip.htm


#7

On the title of this thread, note that GPRS is generally considered to be 2.5G - not 3G…


#8

Many thanks for the great tutorial and advice. :stuck_out_tongue: