how to parse http request in c++

Question

I'm trying to write a small c++ webserver which handles GET, POST, HEAD requests. My problem is I don't know how to parse the headers, message body, etc. It's listening on the socket, I can even write stuff out to the browser just fine, but I'm curious how should I do this in c++.

Afaik a standard GET/POST request should look something like this:

GET /index HTTP/1.1
Host: 192.168.0.199:80
Connection: keep-alive
Accept: */*
User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.22 (KHTML, like Gecko)     Chrome/25.0.1364.97 Safari/537.22
Accept-Encoding: gzip,deflate,sdch
Accept-Language: en-US,en;q=0.8
Accept-Charset: ISO-8859-1,utf-8;q=0.7,*;q=0.3

this is the message body

All lines ended with '\r\n'.

Should I just split the request at '\n' and trim them (and if so how)? Also how to handle files in post data?

Main thing I want to achieve is to get a vector containing headers key=>value pairs, a string with request method, the post data (like in PHP, if it's present), and the query string (/index for example) as string or vector splitted by '/'.

Thanks!

It's an overkill to handle web stuff with C++. But if you really want to go that far you better be ready for way harder string manipulation than this one. — sh03
– sh03, Commented Mar 3, 2013 at 14:46
If you want to parse HTTP messages, the only question you need to ask is ... How many times must I read RFC 2616 before it all sinks in? — user895378
– user895378, Commented Mar 4, 2013 at 13:48
Do you want to write your own server as an exercise or do you want to use a web server library from within C++? In that case, there are very good solutions out there — Konrad Rudolph
– Konrad Rudolph, Commented Apr 19, 2013 at 15:38

masoud · Accepted Answer · 2019-10-30 09:31:01Z

Before doing everything yourself, I introduce you Poco:

class MyHTTPRequestHandler : public HTTPRequestHandler
{
public:
    virtual void handleRequest(HTTPServerRequest & request,
                               HTTPServerResponse & response) {
        // Write your HTML response in res object
    }
};

class MyRequestHandlerFactory : public HTTPRequestHandlerFactory
{
    MyHTTPRequestHandler handler;

public:
    MyRequestHandlerFactory(){}
    HTTPRequestHandler* createRequestHandler(const HTTPServerRequest& request)
    {
        const string method = request.getMethod();
        if (method == "get" || method == "post")
            return &handler;
        return 0;
    }
};

int main()
{
    HTTPServerParams params;
    params.setMaxQueued(100);
    params.setMaxThreads(16);
    ServerSocket svs(80);
    MyRequestHandlerFactory factory;
    HTTPServer srv(&factory, svs, &params);
    srv.start();
    while (true)
        Thread::sleep(1000);
}

sh03 · Accepted Answer · 2013-04-19 15:26:58Z

2

Yes, this is basically just string parsing and then the response creating that goes back to the browser, following the specification.

But if this is not just an hobby project and you do not want to take on a really big task you should use either Apache, if you need a web server you need to extend, or tntnet, if you need a c++ web framework, or cpp-netlib if you need C++ network stuff.

edited Apr 19, 2013 at 15:26

sh03

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answered Mar 2, 2013 at 21:10

Ferenc Deak

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Comments

Konrad Rudolph · Accepted Answer · 2013-04-19 15:44:40Z

2

Boost.Asio is a good library but relativel low-level. You’ll really want to use a higher level library. There’s a modern C++ library called node.native which you should check out. A very server can be implemented as follows:

#include <iostream>
#include <native/native.h>
using namespace native::http;

int main() {
    http server;
    if(!server.listen("0.0.0.0", 8080, [](request& req, response& res) {
        res.set_status(200);
        res.set_header("Content-Type", "text/plain");
        res.end("C++ FTW\n");
    })) return 1; // Failed to run server.

    std::cout << "Server running at http://0.0.0.0:8080/" << std::endl;
    return native::run();
}

It doesn’t get much simpler than this.

answered Apr 19, 2013 at 15:44

Konrad Rudolph

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Comments

firebush · Accepted Answer · 2014-11-19 16:22:08Z

2

You may want to consider Proxygen, Facebook's C++ HTTP framework. It's open source under a BSD license.

answered Nov 19, 2014 at 16:22

firebush

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