How to get the HTTP response string using Curl in C++

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没有蜡笔的小新
没有蜡笔的小新 2021-02-09 22:48

I\'m very new to HTTP commands and the libcurl library. I know how to get the HTTP response code but not the HTTP response string. Following is the code snippet that I wrote to

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  •  说谎
    说谎 (楼主)
    2021-02-09 23:30

    There doesn't look to be much wrong with your code. I ran the following code, based on yours, to read the front page of the BBC news website:

    #include 
    #include 
    #include 
    
    size_t WriteCallback(char *contents, size_t size, size_t nmemb, void *userp)
    {
        ((std::string*)userp)->append((char*)contents, size * nmemb);
        return size * nmemb;
    }
    
    int main(int argc, char * argv[])
    {
        curl_global_init(CURL_GLOBAL_ALL);
    
        CURL* easyhandle = curl_easy_init();
        std::string readBuffer;
    
        curl_easy_setopt(easyhandle, CURLOPT_URL, "http://www.bbc.co.uk/news");
        curl_easy_setopt(easyhandle, CURLOPT_VERBOSE, 1L);
        curl_easy_setopt(easyhandle, CURLOPT_PROXY, "http://my.proxy.net");   // replace with your actual proxy
        curl_easy_setopt(easyhandle, CURLOPT_PROXYPORT, 8080L);
        curl_easy_setopt(easyhandle, CURLOPT_WRITEFUNCTION, WriteCallback);
        curl_easy_setopt(easyhandle, CURLOPT_WRITEDATA, &readBuffer);
    
        curl_easy_perform(easyhandle);
    
        std::cout << readBuffer << std::endl;
    
        return 0;
    }
    

    ... and I got the full HTML response. NB I had to use a proxy, and I enabled verbose mode to see what was happening. Also NB; the HTTP server might be fussy about the URL you give it: if I replace http://www.bbc.co.uk/news with http://www.bbc.co.uk/news/ (i.e. with a trailing slash) then I get no data back (a response length of zero), as noted by the verbose curl output:

    Host: www.bbc.co.uk
    Accept: */*
    Proxy-Connection: Keep-Alive
    
    < HTTP/1.1 301 Moved Permanently
    < X-Cache-Action: PASS (no-cache-control)
    < Vary: Accept-Encoding
    < X-Cache-Age: 0
    < Content-Type: text/html;charset=utf-8
    < Date: Mon, 10 Jul 2017 16:42:20 GMT
    < Location: http://www.bbc.co.uk/news
    < X-XSS-Protection: 1; mode=block
    < X-Content-Type-Options: nosniff
    < X-Frame-Options: SAMEORIGIN
    < Content-Length: 0
    < X-Cache: MISS from barracuda1.[my proxy].net
    < Connection: keep-alive
    < 
    * Connection #0 to host [my proxy] left intact
    

    Here, Content-Length is 0 and the WriteCallback() function is never called. Hope this helps.

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