HTTP POST problem - receive an OK reply but no data arrives


I’m trying to get HTTP POST working with an Open AT application.

I took the standard “HTTP GET” sample, changed the request type to HTTP POST and added some code in http_ClientTestDataHandler() to write the actual data.

I’ve tried three different web hosts (2 x linux Apache and one x IIS7) with a test PHP script that prints out all the GET/POST variables. I have tested my php script using a simple HTML form which posts things to the same test script and it works properly on all hosts - showing a list of all the GET/POST variables.

When I try it from the Wavecom modem (Fastrax Supreme with firmware R74) I get a response of 200 (OK) but the script doesn’t show as having received any data.

I’ve tried lots of variations

  • using HTTP/1.0 and HTTP/1.1
  • setting/leaving out the content length
  • adding extra “host” headers

If I get the content length wrong the web server returns an error. On some web hosts using HTTP/1.1 makes Snort (intrusion prevention s/w for linux boxes) blacklist the IP address for 24 hours because it thinks I’m doing a chunked encoding attack. On other servers HTTP/1.1 works fine. I’ve managed to get an “OK” response on all 4 servers but I never get any data to my PHP script.

I have no idea what I am doing wrong! I feel it should be simple to post some data to a form but I’ve spent days on this already.

The sample HTML form is at (link removed)
The destination php page is at: (link removed).

The code I have is as follows:

In http_ClientTestDataHandler()

		TRACE(( 4, "http_ClientTestDataHandler: WIP_CEV_WRITE\n" ));
		adl_atSendResponse ( ADL_AT_UNS, "\r\nhttp_ClientTestDataHandler: WIP_CEV_WRITE\r\n");

		wm_sprintf(info, "abcef=12345678901234"); // 20 bytes long

		BytesWritten = wip_write( pHttpClientCtx->DataChannel, info, 20);
		if(BytesWritten < 0)
		{/* error */
			//wip_debug( "HTTP write error %i\n", BytesWritten);
			adl_atSendResponse ( ADL_AT_UNS, "\r\nwip_write error\r\n" );
			TRACE(( 4, "http_ClientTestDataHandler: bytes %d written\n", BytesWritten ));
			wm_sprintf( info, "\r\nhttp_ClientTestDataHandler: %d bytes written\r\n", BytesWritten);
			adl_atSendResponse ( ADL_AT_UNS, info);
		wip_shutdown( pHttpClientCtx->DataChannel, FALSE, TRUE);

In http_ClientTestCreate (original error now fixed in case someone does a cut/paste in the future for a HTTP POST example)

static s32 http_ClientTestCreate(void)
  s32 ret = 0;

  // HTTP Session creation
  // ---------------------------
  http_ClientTestCtx.CnxChannel = wip_HTTPClientCreateOpts(

                    NULL,  // no handler
                    NULL,  // no context

                    // default headers
//                    WIP_COPT_HTTP_VERSION, WIP_HTTP_VERSION_1_0,
                    WIP_COPT_HTTP_HEADER, "User-Agent", "WIPHTTP/1.0",


  if (http_ClientTestCtx.CnxChannel == NULL)
    TRACE(( 1, "cannot create http session channel\n" ));
    adl_atSendResponse ( ADL_AT_UNS, "cannot create http session channel\r\n" );
    ret = -1;
    // HTTP GET command
    // ---------------------------
    http_ClientTestCtx.DataChannel = wip_getFileOpts(

                    http_ClientTestCtx.CnxChannel,  // session channel

                    HTTP_STR_URL,                   // requested URL

                    http_ClientTestDataHandler,     // data handler
                    &http_ClientTestCtx,            // context

                    // request headers
                    WIP_COPT_HTTP_HEADER, "Content-Type", "application/x-www-form-urlencoded",
                    WIP_COPT_HTTP_HEADER, "Content-Length", "20",


    if (http_ClientTestCtx.DataChannel == NULL)
      TRACE(( 1, "cannot create http data channel\n" ));
      adl_atSendResponse ( ADL_AT_UNS, "cannot create http data channel\r\n" );
      wip_close( http_ClientTestCtx.CnxChannel);
      ret =-1;


The PHP script is

	function ReturnArrayKeysAndValues($pArray)
		$ReturnString = "";
		if (is_array($pArray))
			while($ArrayCell = each($pArray))
				$ReturnString .= "Key: " . $ArrayCell["key"] . "\tValue: " . $ArrayCell["value"] . "\r\n";
			} // while
	$Body .= "\r\nPOST Array\r\n";
	$Body .= ReturnArrayKeysAndValues($_POST);

	$Body .= "\r\nGET Array\r\n";
	$Body .= ReturnArrayKeysAndValues($_GET);

	$Body .= "\r\nSERVER Array\r\n";
	$Body .= ReturnArrayKeysAndValues($_SERVER);

	print $Body;

The HTML Page is:

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "">
<html xmlns="">
<head>  <title></title> </head>
 <FORM action="http://your URL/PostTest1.php" method="post">
    <P>First name: <INPUT type="text" name="firstname"><BR> Last name: <INPUT type="text" name="lastname"><BR>  <INPUT type="submit" value="Send"> <INPUT type="reset">  </P>


Have you read HTTP made Really Easy?

Try using the following php code to read the POST variables and echo them back as a formatted array:

	echo "<pre>PostData<br>"; print_r($_POST); echo "</pre>";

Also, what Operator are you using? There’s some posts here on the forum that indicate not all Operators pass POST data through their networks properly :frowning:

ciao, Dave

Thanks to John & Andrew at M2M Communications I’ve now got it working.

They found that I had left the double quotes off the “Content-Length” header value - ie I had

WIP_COPT_HTTP_HEADER, "Content-Length", 20,

instead of

WIP_COPT_HTTP_HEADER, "Content-Length", "20",