Connecting with GPRS

opvini · Joined: 27 Apr 2012 Posts: 50 Location: Brazil

Hi,
I have a GSM module (SIM340), and I need to connect my PIC18F4520 with GPRS to send data (to my web-server) and to RECEIVE data (from my web-server using sockets), like a server.

Well, I can send SMS, receive SMS, receive call and I can send data with GPRS, but I can't receive.

I am using the AT commands to connect and send data, like bellow:

ckielstra · Joined: 18 Mar 2004 Posts: 3680 Location: The Netherlands

Most likely the problem is with your cellular provider.
As I understand from your device you can setup a data connection to any address on the internet? This is called a Mobile Originated service. What you are looking for is a service called Mobile Terminated.

Your cellular provider has only a limited number of IP-addresses and will use NAT (Network Address Translation) to make the connection from your mobile to the internet. Setting up a connection in the other direction, from internet to your mobile, won't work because the required entry in the NAT is missing.

The solution is to ask your cellular provider for a wireless plan (APN) that supports Mobile Terminated Data. In such a plan your mobile will be designated a fixed IP-address (and no NAT is required anymore) or you will be given a range of TCP-ports (added as static routes to the NAT).

E_Blue · Joined: 13 Apr 2011 Posts: 417

If you receive an IP, 117.98.109.172 in your example, you are already connect, so What do you mean with you can't connect?

I'm curious, Why do you choose Server mode from SIM340?

As I understand the server mode is to wait a connection from anybody who send data to the designated port, not to start one.

If you need to connect to one web address I think that you must to use Client mode.
In Client mode you can connect from one to several IP address.
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Electric Blue

opvini · Joined: 27 Apr 2012 Posts: 50 Location: Brazil

Hi, thanks for reply.
Well, I need work with the client mode and the server mode, becouse I need to send data from time to time, for example with a period of 5s, and, simultaneously I need to listen one port to receive data anytime from others...

opvini · Joined: 27 Apr 2012 Posts: 50 Location: Brazil

is it possible? Work with server mode and client mode simultaneously?

E_Blue · Joined: 13 Apr 2011 Posts: 417

I think not.

You must choose one of them.

I don't remember about SIM340 but in SIM900 it exist something called MUX MODE.
In that mode you can be a client connected to several IPs at same time.

Read the datasheet, may be it help you.
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Electric Blue