GPRS connection

[manaila]

Hi,

I want to establish a simple HTTP connection from my PC to a remote server via GPRS, using the C code shown below. This libcurl code from libcurl - simple.c works fine when using ethernet connection, but when using GPRS it fails.
NOTE: -ttyS1 is the GSM modem attached to the PC
-the header file which define ttyS1 and write function is not shown

#include <stdio.h>
#include <curl/curl.h>
 
int main(void)
{
    CURL *curl;
    CURLcode res;
    int i=0;
     
    while(i<2)
    {
        write(ttyS1,"ATE0\r\n",strlen("ATE0\r\n"));//no echoeing
        sleep(1);
        write(ttyS1,"AT+CGATT?\r\n",strlen("AT+CGATT?\r\n"));
        sleep(1);
        write(ttyS1,"AT+CIFSR\r\n",strlen("AT+CIFSR\r\n"));
        sleep(1);
        write(ttyS1,"AT+CIPMODE=0\r\n",strlen("AT+CIPMODE=0\r\n"));
        sleep(1);
        write(ttyS1,"AT+CIPCSGP=1,\"MyISP\"\r\n",strlen("AT+CIPCSGP=1,\"ETL\"\r\n"));
        sleep(1);
        curl = curl_easy_init();
        if(curl) 
        {
             curl_easy_setopt(curl, CURLOPT_URL, "http://www.example.com");
                res = curl_easy_perform(curl);
         
                /* always cleanup */ 
                curl_easy_cleanup(curl);
        }
        i++;
    }
    write(ttyS1,"AT+CIPCLOSE\r\n",strlen("AT+CIPCLOSE\r\n"));
    sleep(1);
    return 0;
}

Can you help me on how I can establish a GPRS connection to a remote server using AT commands in a C code so that I can be able to test the connection by, for instance, pinging the remote server.

cheers