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POC or C++ HTTP daemon in a thread?
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  1. POC or C++ HTTP daemon in a thread?
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    copied!<p>I'm starting up a new embedded system design using FreeRTOS. My last one used eCos, which has a built-in HTTP server that's really lightweight, especially since I didn't have a filesystem. The way it worked, in short, was that every page was a CGI-like C function that got called when needed by the HTTP daemon. Specifically, you would write a function of the form:</p> <pre><code>int MyWebPage(FILE* resp, const char* page, const char* params, void* uData); </code></pre> <p>where <code>page</code> was the page part of the url, <code>params</code> were any form parameters (only GET was supported, not POST, which prevented file uploads and thus made burning the flash a pain), <code>uData</code> is a token passed in that was set when you registered the function, so you could have the same function serve multiple URLs or ranges with different data, and <code>resp</code> is a file handle that you write the HTTP response (headers and all) out to.</p> <p>Then you registered the function with:</p> <pre><code>CYG_HTTPD_TABLE_ENTRY(www_myPage, "/", MyWebPage, 0); </code></pre> <p>where <code>CYG_HTTPD_TABLE_ENTRY</code> is a macro where the first parameter was a variable name, the second was a page URL (the <code>*</code> wildcard is allowed; hence <code>page</code> getting passed to <code>MyWebPage()</code>), third is the function pointer, and last is the <code>uData</code> value.</p> <p>So a simple example:</p> <pre><code>int HelloWorldPage(FILE* resp, const char*, const char* params, void*) { fprintf("Content-Type: text/html;\n\n"); fprintf("&lt;html&gt;&lt;head&gt;&lt;title&gt;Hello World!&lt;/title&gt;&lt;/head&gt;\n"); fprintf("&lt;body&gt;\n"); fprintf("&lt;h1&gt;Hello, World!&lt;/h1&gt;\n"); fprintf("&lt;p&gt;You passed in: %s&lt;/p&gt;\n", params); fprintf("&lt;/body&gt;&lt;/html&gt;\n"); } CYG_HTTPD_TABLE_ENTRY(www_hello, "/", HelloWorldPage, 0); </code></pre> <p>(Actually, <code>params</code> would be passed through a function to escape the HTML magic characters, and I'd use another couple functions to split the params and make a <code>&lt;ul&gt;</code> out of it, but I left that out for clarity.)</p> <p>The server itself just ran as a task (i.e. thread) and didn't get in the way as long as it had a lower priority than the critical tasks.</p> <p>Needless to say, having this proved invaluable for testing and debugging. (One problem with embedded work is that you generally can't toss up an XTerm to use as a log.) So when Supreme Programmer reflexively blamed me for something not working (path of least resistance, I guess), I could pull up the web page and show that he had sent me bad parameters. Saved a lot of debug time in integration.</p> <p><em>So anyway...</em> I'm wondering, <strong>is there something like this available as an independent library?</strong> Something that I can link in, register my callbacks, spawn a thread, and let it do the magic? Or do I need to crank out my own? I'd prefer C++, but can probably use a C library as well.</p> <p>EDIT: Since I'm putting a bounty on it, I need to clarify that the library would need to be under an open-source license.</p>
 

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