Hello,
This is a general explanation on how to connect to internet from a GSM/GPRS.
The AT command AT+CGDATA=1 is supposed to activate all what is needed in your GSM to
make an attachement procedure as GPRS. ( Otrherwise, do AT+CGATT=1, AT+CGACT=1, and dont forget to set the APN name with AT+CGDCONT+....)
From there, the MODULE (gsm module or gsm phone) send you some frame because he try to
negociate some parameters with you to get the connection working properly.
What you see on the reply like
CONNECT 115200
~ }#À!}!}!} }6}!}$}%Ü}"}&} } } } }'}"}(}"}#}$À#&´~
are ASCII characters who can bee converted in Hexadecimal.
All the documentation about internet frames are explained in hexa. As an example, if you convert the above frame you get
7EFF03C02101010016010405DC020600000000070208020304C02326B47E
this is an LPC frame decoded as here below:
7E : StartFlag
FF : addr
03 : controle
C021 : protocole LCP
01 : code Configure-Request
01 : identifier
0016 : Frame lenght
01 : option MRU
04 : option lenght
05 : data
DC : data
02 : option ACCM
06 : option lenght
00 : data
00 : data
00 : data
00 : data
07 : option Protocol Compression
02 : option lenght
08 : option Address and Control Field Compression
02 : option lenght
03 : option Authentication Protocol
04 : option lenght
C0 : data
23 : data
26B4 : Frame Check sequence
7E : end flag
You have to make some replay to those sentences, as well as the other coming after, in order to negociate a connection between you GSM and the Internet World, via the APN of your provider.
Usually, the connection begin with a PPP negociation, followed by a authenticate cession like PAP or CHAP, then an IPCP exchange, getting the necessary IP adresse and DNS name in order to transmit and receive IP frames on the internet.
There are very detailled explanation of the PPP, PAR CHAP IP frame that you can find on
The TCP/IP Guide - The TCP/IP Guide
Philippe