GPRS HTTP 400 Bad request

at commandsavrgprsgsm

I am facing some problem with GPRS Project. I am sending request to server through GPRS and receiving responce from the server.
I have used AVR ATmega32 micro controller and SIM900 GSM/GPRS Module from simcom.
I can send HTTP Request Header Successfully to the server, but getting Bad Request response every time.
I have wrote program in AVR Studio 6.2.
here I have attached Response of Server received on GPRS.

  AT
OK
AT+CSMINS?
+CSMINS: 0,1

OK
AT+CREG?
+CREG: 0,1

OK
AT+CGATT?
+CGATT: 1

OK
AT+CIPSHUT
SHUT OK
AT+CIPSTATUS
OK

STATE:IP INITIAL
AT+CIPMUX=0
OK
AT+CSTT="idea gprs"
OK
AT+CIICR
OK
AT+CIFSR
10.112.37.103
AT+CIPSTART= "TCP","198.136.54.34","80"
OK

CONNECT OK
AT+CIPSEND
> GET /httptest.php?data1=value1 HTTP/1.1
 Host: http://exqure.com


SEND OK
HTTP/1.1 400 Bad Request
Date: Thu, 18 Jun 2015 12:19:34 GMT
Server: Apache
Content-Length: 226
Connection: close
Content-Type: text/html; charset=iso-8859-1

<!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML 2.0//EN">
                                                  <html><head>
                                                              <title>400 Bad Request</title>
                 </head><body>
                              <h1>Bad Request</h1>
                                                  <p>Your browser sent a request that this server could not understand.<br />
                                                  </p>
                                                      </body></html>

I want to under stand that where I am going wrong? What is the correct format for HTTP header request?

Here is my Code :

//////////////////////////////////////////////////////////////////////////
//          SEND DATA
//////////////////////////////////////////////////////////////////////////
    LCD_ClearScreen();
    LCD_goto_XY(1,1);
    LCD_Print("Sending DATA");
    _delay_ms(1000);
    LCD_ClearScreen();
    r=SIM300SendDATA(0,"/httptest.php?data1=value1","http://exqure.com");
    if (r==SIM300_FAIL)
    {


    }

int8_t  SIM300SendDATA(uint8_t *Method,char *PATH,char *HOST)
{
    UFlushBuffer();
    //UWriteString(num);
    char cmd[25]="AT+CIPSEND",DataToSend[255];
    //char GET2[255]="";
    //char CRLF[4]="\r\n\r\n";
    //Send Command
    SIM300Cmd(cmd);

    _delay_ms(200);
    uint8_t len = SIM300GPRSWaitForResponse(1000);
    if(len)
    {
        if (!Method)
        {
            sprintf(DataToSend, "GET %s HTTP/1.1\r\n Host: %s\r\n\r\n", PATH, HOST);
        }
        else
        {
            sprintf(DataToSend, "POST %s HTTP/1.1\r\n Host: %s\r\n", PATH,HOST);
        }
    }
    else
    {
        return SIM300_TIMEOUT;
    }


    UWriteString(DataToSend);
    //UWriteString(GET2);
    //UWriteString(CRLF);
    UWriteData(0x1A);

    len=SIM300WaitForResponse(1000);

    if(len==0)
    return SIM300_TIMEOUT;

    sim300_buffer[len-1]='\0';

    if(strncasecmp(sim300_buffer+2,"CMGS:",5)==0)
    {
        UFlushBuffer();

        return SIM300_OK;
    }
    else
    {
        UFlushBuffer();
        return SIM300_FAIL;
    }
}

Best Answer

I solved the problem. :) The problem was with Extra "Space" in header.

sprintf(DataToSend, "GET %s HTTP/1.1\r\n Host: %s\r\n\r\n", PATH, HOST);

I removed that space:

sprintf(DataToSend, "GET %s HTTP/1.1\r\nHost: %s\r\n\r\n", PATH, HOST);

and then problem get resolved. here is the response from server:

HTTP/1.1 200 OK
Date: Fri, 19 Jun 2015 03:38:14 GMT
Server: Apache
X-Powered-By: PHP/5.4.34
Cache-Control: no-store, no-cache, must-revalidate, post-check=0, pre-check=0
Pragma: no-cache
Last-Modified: Fri, 19 Jun 2015 03:38:14 GMT
Vary: Accept-Encoding,User-Agent
Content-Length: 87
Content-Type: text/plain

This is REQUEST Data
data1:value1
This is GET Data
data1:value1
This is POS
           HTTP/1.1 200 OK
Date: Fri, 19 Jun 2015 03:38:14 GMT
Server: Apache
X-Powered-By: PHP/5.4.34
Cache-Control: no-store, no-cache, must-revalidate, post-check=0, pre-check=0
Pragma: no-cache
Last-Modified: Fri, 19 Jun 2015 03:38:14 GMT
Vary: Accept-Encoding,User-Agent
Content-Length: 87
Content-Type: text/plain

This is REQUEST Data
data1:value1
This is GET Data
data1:value1
This is POS
           T Data

Thanks guys.

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Electronic – Signal the MCU using GPRS

In principle an GPRS modem can listen to a socket for incoming connections but there are a few problems in practice:

Most network providers don't give you an externally routable IP address and if they do they are often firewalled. Depending on the provider getting a routable address may be a free option, a paid extra or not available at all.
If you get a routable address the IP address will normally be dynamic so you need to take care of keeping track of the external address, maybe say using a dynamic DNS providers which then you must write software for (although fairly simple) to keep it updated.

I find that the most reliable method that works across all networks is to poll the server (in this case your laptop) and retrieve any messages.You seem to have communications sorted out in that direction and many modems have varying AT enhancements to make it easier so I'll stick with a broad description of a system I did a while back:

Every 5 minutes the remote unit sends an HTTP POST to the server that sends any outstanding data (even if there is none). The server sends back an HTTP response to indicate that the data was received that also includes any messages destined for the unit. Part of that response also includes a last message sequence number that is sent in the next POST so that the server knows what messages have been previously received and processed OK by the remote unit.

You could also take a look at GSM push notifications, I've never used them myself but believe they are SMS based and their configuration is somewhat network dependent.

Electronic – GSM/GPRS AT command – hitting a link

You're opening the socket OK but the part you're missing is that you'll need to issue an HTTP request to the server. The full documentation you'll probably want to look at is RFC2616 but the request should look roughly like this:

GET /SUB/PAGE.PY HTTP/1.1
Host: www.MYSERVR.com
(blank line)

The above probably violates a few standards because there are additional headers I believe you should include, but it should give you a pointer in the right direction. Maybe for a start install a Telnet client and try connecting that way rather than using a web browser so you can check that the request works OK and easily check the response you get back.

You need to send the above over the socket, so for that module take a look at AT+AIPW command.

Best Answer

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