I have a DT80 in a remote area with only GPRS network available. Through GPRS, I want to open the remote DT80 web page. I cannot install a GPRS static IP on the DT80 because it cost $500 in my country and none of my customers can afford it.

So I am thinking of using existing dynamic GPRS and DDNS (dyndns.com). However from my existing noobish GPRS understanding, this system will not work. Have you guys got this working before? Can you check if my understanding below have any error?

1. I got the below ordinary USB wireless modem people normally use for internet browsing. I plug USB wireless modem to my laptop. I go to whatismyip.com, it shows the IP address 220.255.7.139.

   I type ipconfig, it shows the IP address is 119.234.164.229! So why is the two IP address shown is different? I as a noob thinks that whatismyip.com is showing the gateway address of my USB modem GPRS network visible to the internet.
   And ipconfig is showing the IP address of my USB modem inside the GPRS APN but not visible to internet. Is my understanding correct at this point?

2. I then unplug and plug the USB modem, check the ipconfig, and repeat. I notice each time the IP address shown in ipconfig is different.

   This shows that the modem IP inside the GPRS APN is a dynamic IP, not a static IP. Is my understanding correct for point 2?

3. I unplug and plug the USB modem, and check whatismyip.com. I notice the each time IP address shown in whatismyip.com is different.

   This shows that my USB modem gateway is appearing as a dynamic IP address in the internet, not a static IP as one noob would intuitively think. Is my understanding correct for point 3?

4. So below is my overall understanding of my USB modem core GPRS network architecture. Is my conceptual understanding correct?

5. Now from my understanding, DDNS would only work if DT80 has static IP inside the APN. If DT80 has dynamic IP inside the APN, from my understanding above, the DDNS cannot find the dynamic IP in the GPRS APN, because dyndns.com is in the internet world, there is no DDNS in the GPRS APN.

   So DDNS will not work if DT80 is in a GPRS dynamic IP network. If my DT80 is not on a GPRS network with dynamic but instead on the internet. I hook up a ordinary router to the internet and assign a static IP from the router to DT80, this will work with dyndns.com.

So what you guys think?
orange

Dear Orange,

I don't know how USB modems work, two suppositions:

1. USB modem act as a sort of bridge; with the ipconfig command you read the "internal" IP address established via PPP between the driver and the "internal" private interface.
2. More likely is your mobile provider doing the bridging operations.

This doesn't explain why the assigned IP is in the public class. In my opinion you have to make a call to your mobile phone operator and ask the following:

• What type of dynamic IP address do you assign to me (public / private)?
• Is the address accessible for external connection?
• Do I have some limitations in using it?

If the dynamic assigned IP address is a public one without other limitation, I think that DT80 may me be connected from the "outside" using GPRS router (with DDNS service). If what I've written has sense

I hope that can help.

Regards

Good morning All,

While I'm not sure of exactly how DDNS works basically what happens is DT80 will contact the DDNS server and the server will identify the dynamic TCP/IP address assigned to the logger.

The same with the computer, when it contacts DDNS server, it will identify your computers TCP/IP address then the service makes the logical link between the two. All you really need to know is some magic happens and it works.

Cheers,
Roger

You will find that the GPRS network uses a public IP and then you have your dynamic IP behind that. So there is a public firewall in the middle.

Vodafone do the same here in Australia.

What modem you using? Sierra Wireless?

So you never got DDNS to work with GPRS in Australia? Have you got it to work in the USA or somewhere else?

orange

Dynamic DNS works okay, but not always well enough for some. The best thing is to try it and see if it suits you.

Hi,

I had similar issues, and worked with a service provider which supplied me with a separate APN, and then provided a publicly accessible IP address.

This, combined with a GPRS broadband router, which established an automatic PPP link, and which ad the facility for routing tables, allow me to directly access both the port 7700 from a friendly IP only (i have a fixed office IP) and the web interface from a specific range.

I should point out that there is a significant power implication of using the Ethernet port on remote equipment which, if solar powered, can require a substantial battery and panel array as you will probably be using the logger with the unit ON all the time, and also the router will sap about 500 mW, and if powered by the SSPWR then there is an additional overhead.

In the UK I used Wireless Logic. I would imagine there are similar in most countries. If you use a standard sim and establish a PPP connection, then this will only be within your service providers network, and they will route traffic from the private IP and the internet.

On the same note, as i have some units in remote areas with GPRS and FTP Push enabled, i have found that using the 1RELAY command to switch power through the relay to turn on the router, and then turn it off later is variable. The operation of 1RELAY is not reliable.

If anyone can suggest whats wrong here, i would be interested, but would also stress that this spans across multiple systems with different applications, and the one i demonstrate here is merely an example. I have found the relay to be consistently unreliable across programs, applications and loggers (DT80/85).

RE1H
ALARM2(T>12:00:00){XF}
ALARM3(T>15:00:00){XG}

RFX
1RELAY=1

RFG
1RELAY=0

Using the above, i have found that the relay does not disengage and that this causes rapid power issues on my systems.

Best Regards All,
Peter

Many thanks to you guys for the experience and tips.

orange

Good afternoon Peter,

We haven't had any reports of the relay being unreliable, we need to look into this further. Can you please email me directly so we can look into this in greater detail?

We can reduce your command to one line by putting 1RELAY after the trigger definition, e.g:

RE1H
ALARM2(T><12:00:00,15:00:00)1RELAY

The output 1RELAY will take on the truth of the alarm. That is when the alarm is true (1) 1RELAY=1 when the alarm is false (0) then 1RELAY=0

Cheers,
Roger