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POSend CGI request from C++ program?
 

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    <p>I am currently working on integrating a prototype product I made into a larger program. What I did in the prototype was create a HTTP server on a microcontroller, and then wrote some HTML to call .cgi functions on the web-server. This was so I could control I/O on the micro controller via an ethernet. </p> <p>My html seems very straight forward, to call a cgi function on the microcontroller I have made buttons with the following syntax:</p> <pre><code>&lt;script type="text/javascript"&gt; function my_confirm(a){ var r=confirm("Are you sure you'd like to run "+a+"?"); if (r==true) location.href = a; } &lt;/script&gt; &lt;button type = "button" onclick=" my_confirm('started.cgi')" &gt;Started&lt;/button&gt; </code></pre> <p>additionally, if i were to type in "169.254.129.12/started.cgi" into a web browser, the microcontroller would respond appropriately. Now that the prototype is completed ahead of schedule, my new task is to integrate my controls into a C++/CLI program. GREAT. I have never written in C++... </p> <p>Rather than re-doing all of the backend stuff, I would like to add a menu to send similiar requests. Over the last 4-5 days I have gotten a menu in VS2005 and have had limited success, with the code below:</p> <pre><code>int sendHttpRequestAndRespond(System::Uri^ url){ if(url-&gt;Scheme == System::Uri::UriSchemeHttp){ HttpWebRequest^ request = dynamic_cast&lt;HttpWebRequest^&gt;(WebRequest::Create(url)); request-&gt;Method = System::Net::WebRequestMethods::Http::Get; return 0; } //HttpWebResponse^ response = dynamic_cast&lt;HttpWebResponse^&gt; (request-&gt;GetResponse()); //RequestState^ state = gcnew RequestState(); //state-&gt;request = request; //try{ // IAsyncResult^ response = dynamic_cast&lt;IAsyncResult^&gt; (request-&gt;BeginGetResponse(gcnew AsyncCallback( responseReceived),state)); //} //catch(WebException^ e){} else return -1; } </code></pre> <p>With the code written as shown above(with comments present) the I/O control of the microcontroller does not operate properly. Oddly, if I put in the HttpWebResponse line, things (sometimes) go properly, and other times, nothing seems to happen. Lastly, if I use the AsyncResponse, things are similiar to if I use the HttpWebResponse portion.</p> <p>Now my thought/understanding was that merely putting in the request via the GET method I am using in the code shown above would initiate the I/O control on the microcontroller, but it seems the response plays a role in it as well.</p> <p>Do any of you have a better route to go with this? At this point I am highly confused/frustrated and open to any advice! Thank you,</p> <p><strong>EDIT 1: UPDATED CODE:</strong></p> <pre><code>int sendHttpRequestAndRespond(System::Uri^ url){ if(url-&gt;Scheme == System::Uri::UriSchemeHttp){ HttpWebRequest^ request = dynamic_cast&lt;HttpWebRequest^&gt;(WebRequest::Create(url)); request-&gt;Method = System::Net::WebRequestMethods::Http::Get; RequestState^ state = gcnew RequestState(); state-&gt;request = request; try{ IAsyncResult^ response = dynamic_cast&lt;IAsyncResult^&gt; (request-&gt;BeginGetResponse(gcnew AsyncCallback( responseReceived),state)); } catch(WebException^ e){} return 0; } </code></pre> <p>With this code I get into my callback function (responseReceived) the first two times I call the function, but never on the 3rd or further time. I am testing this with <a href="http://www.facebook.com" rel="nofollow">http://www.facebook.com</a>, as this seems to work for my CGI calling, but only the first two times as well. Thanks,</p> <p><strong>EDIT 2: Resolution and new problems!</strong> Okay, I figured out my problem was due mostly to not ending the requests. In the callBack function I wasn't ending the request, and HTTP protocol has a 2 connections/ip restriction, making the first two calls work, but future ones wouldn't. </p> <p>Now my new issue is that on the asyc call I a using, it first does synchronous DNS resolution. Since I am sending these commands to an embedded computer with an IP, there's no DNS inbetween, and the function blocks for a long time. Once my computer realizes there's been a DNS resolution error, it fires off the request any ways, and it works! Subsequent requests work instantly, as there's a cache that remembers the failure. </p> <p>So im about 99% of the way there, but I need to fix this first time lockup some how. My current ideas are:</p> <p>Somehow disable dns resolution before the request</p> <p>Shorten the dns resolution timeout from 60+ seconds to 1ish seconds</p> <p>trick my comptuer/the computer the program runs on into thinking that <a href="http://169.254.129.12" rel="nofollow">http://169.254.129.12</a> has an ip address of 169.254.129.12 (local host file??)</p> <p>I am not sure how to accomplish those, or if there are better ideas??</p> <p>Thank you,</p> <p>Any better ideas?</p>
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