C语言中的简单HTTP请求和响应

时间：2016-06-27 13:45:15

标签： c

如何用C语言编写简单的HTTP请求和响应。

在Java中我可以使用：

    String url = "http://www.google.com/search?q=mkyong";

    URL obj = new URL(url);
    HttpURLConnection con = (HttpURLConnection) obj.openConnection();

    con.setRequestMethod("GET");

    con.setRequestProperty("User-Agent", USER_AGENT);

    int responseCode = con.getResponseCode();
    System.out.println("\nSending 'GET' request to URL : " + url);
    System.out.println("Response Code : " + responseCode);

    BufferedReader in = new BufferedReader(
            new InputStreamReader(con.getInputStream()));
    String inputLine;
    StringBuffer response = new StringBuffer();

    while ((inputLine = in.readLine()) != null) {
        response.append(inputLine);
    }
    in.close();

我怎样才能使用C语言？

我已尝试Here： 但它没有正常工作。

主要回应：

HTTP/1.1 301 Moved Permanently Location: http://www.google.co.in/ Content-Type: text/html; charset=UTF-8 Date: Mon, 27 Jun 2016 13:53:36 GMT Expires: Wed, 27 Jul 2016 13:53:36 GMT Cache-Control: public, max-age=2592000 Server: gws Content-Length: 221 X-XSS-Protection: 1; mode=block X-Frame-Options: SAMEORIGIN

<HTML><HEAD><meta http-equiv="content-type" content="text/html;charset=utf-8"> <TITLE>301 Moved</TITLE></HEAD><BODY> <H1>301 Moved</H1> The document has moved <A HREF="http://www.google.co.in/">here</A>. </BODY></HTML>

1 个答案:

答案 0 :(得分：1)

您需要一个外部库来解决您的问题，libcurl是一个很好的选择。

试试这段（测试过的）代码：

#include <stdlib.h>
#include <stdio.h>
#include <string.h>

#include <curl/curl.h>


typedef struct string_buffer_s
{
    char * ptr;
    size_t len;
} string_buffer_t;


static void string_buffer_initialize( string_buffer_t * sb )
{
    sb->len = 0;
    sb->ptr = malloc(sb->len+1);
    sb->ptr[0] = '\0';
}


static void string_buffer_finish( string_buffer_t * sb )
{
    free(sb->ptr);
    sb->len = 0;
    sb->ptr = NULL;
}


static size_t string_buffer_callback( void * buf, size_t size, size_t nmemb, void * data )
{
    string_buffer_t * sb = data;
    size_t new_len = sb->len + size * nmemb;

    sb->ptr = realloc( sb->ptr, new_len + 1 );

    memcpy( sb->ptr + sb->len, buf, size * nmemb );

    sb->ptr[ new_len ] = '\0';
    sb->len = new_len;

    return size * nmemb;

}


static size_t header_callback(char * buf, size_t size, size_t nmemb, void * data )
{
    return string_buffer_callback( buf, size, nmemb, data );
}


static size_t write_callback( void * buf, size_t size, size_t nmemb, void * data )
{
    return string_buffer_callback( buf, size, nmemb, data );
}


int main( int argc, char * argv[] )
{
    CURL * curl;
    CURLcode res;
    string_buffer_t strbuf;

    char * myurl = argv[1];

    string_buffer_initialize( &strbuf );

    curl = curl_easy_init();

    if(!curl)
    {
        fprintf(stderr, "Fatal: curl_easy_init() error.\n");
        string_buffer_finish( &strbuf );
        return EXIT_FAILURE;
    }

    curl_easy_setopt(curl, CURLOPT_URL, myurl );
    curl_easy_setopt(curl, CURLOPT_FOLLOWLOCATION, 1L );
    curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, write_callback );
    curl_easy_setopt(curl, CURLOPT_HEADERFUNCTION, header_callback );
    curl_easy_setopt(curl, CURLOPT_WRITEDATA, &strbuf );
    curl_easy_setopt(curl, CURLOPT_HEADERDATA, &strbuf );

    res = curl_easy_perform(curl);

    if( res != CURLE_OK )
    {
        fprintf( stderr, "Request failed: curl_easy_perform(): %s\n", curl_easy_strerror(res) );

        curl_easy_cleanup( curl );
        string_buffer_finish( &strbuf );

        return EXIT_FAILURE;
    }

    printf( "%s\n\n", strbuf.ptr );

    curl_easy_cleanup( curl );
    string_buffer_finish( &strbuf );

    return EXIT_SUCCESS;
}

/* eof */

编译（gcc / linux）：

$ gcc -Wall httpget.c -lcurl -o httpget

测试：

$ ./httpget "http://www.google.com/search?q=mkyong"

输出：

HTTP/1.1 302 Moved Temporarily
Location: http://ipv4.google.com/sorry/IndexRedirect?continue=http://www.google.com/search%3Fq%3Dmkyong%26safe%3Dactive&q=CGMSBL0cgPIYq_vEuwUiGQDxp4NLKiIBT1ZvF-YL0aR4jC6o1OrjEvE
Date: Mon, 27 Jun 2016 14:52:27 GMT
Pragma: no-cache
Expires: Fri, 01 Jan 1990 00:00:00 GMT
Cache-Control: no-store, no-cache, must-revalidate
Content-Type: text/html; charset=UTF-8
Server: HTTP server (unknown)
Content-Length: 368
X-XSS-Protection: 1; mode=block
X-Frame-Options: SAMEORIGIN
X-Cache: MISS from proxy.foobar.com
X-Cache-Lookup: MISS from proxy.foobar.com:80
Via: 1.1 proxy.foobar.com (squid)
Connection: keep-alive

HTTP/1.1 503 Service Unavailable
Date: Mon, 27 Jun 2016 14:52:27 GMT
Pragma: no-cache
Expires: Fri, 01 Jan 1990 00:00:00 GMT
Cache-Control: no-store, no-cache, must-revalidate
Content-Type: text/html
Server: HTTP server (unknown)
Content-Length: 2924
X-XSS-Protection: 1; mode=block
X-Frame-Options: SAMEORIGIN
X-Cache: MISS from proxy.foobar.com
X-Cache-Lookup: MISS from proxy.foobar.com:80
Via: 1.1 proxy.foobar.com (squid)
Connection: keep-alive

<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head><meta http-equiv="content-type" content="text/html; charset=utf-8"><meta name="viewport" content="initial-scale=1"><title>http://www.google.com/search?q=mkyong&amp;safe=active</title></head>
<body style="font-family: arial, sans-serif; background-color: #fff; color: #000; padding:20px; font-size:18px;" onload="e=document.getElementById('captcha');if(e){e.focus();}">
<div style="max-width:400px;">
 <hr noshade size="1" style="color:#ccc; background-color:#ccc;"><br>

  To continue, please type the characters below:<br><br>
  <img src="/sorry/image?id=12134302468701323331&amp;q=CGMSBL0cgPIYq_vEuwUiGQDxp4NLKiIBT1ZvF-YL0aR4jC6o1OrjEvE&amp;hl=en&amp;continue=http://www.google.com/search%3Fq%3Dmkyong%26safe%3Dactive" border="1" alt="Please enable images"><br><br><form action="CaptchaRedirect" method="get"><input type='hidden' name='q' value='CGMSBL0cgPIYq_vEuwUiGQDxp4NLKiIBT1ZvF-YL0aR4jC6o1OrjEvE'><input type="hidden" name="continue" value="http://www.google.com/search?q=mkyong&amp;safe=active"><input type="hidden" name="id" value="12134302468701323331"><input type="text" name="captcha" value="" id="captcha" size="12" style="font-size:16px; padding:3px 0 3px 5px; margin-left:0px;"><input type="submit" name="submit" value="Submit" style="font-size:18px; padding:4px 0;"><br><br><br></form>
  <hr noshade size="1" style="color:#ccc; background-color:#ccc;">

   <div style="font-size:13px;">
    <b>About this page</b><br><br>Our systems have detected unusual traffic from your computer network.  This page checks to see if it&#39;s really you sending the requests, and not a robot.  <a href="#" onclick="document.getElementById('infoDiv').style.display='block';">Why did this happen?</a><br><br>
    <div id="infoDiv" style="display:none; background-color:#eee; padding:10px; margin:0 0 15px 0; line-height:1.4em;">
     This page appears when Google automatically detects requests coming from your computer network which appear to be in violation of the <a href="//www.google.com/policies/terms/">Terms of Service</a>. The block will expire shortly after those requests stop.  In the meantime, solving the above CAPTCHA will let you continue to use our services.<br><br>This traffic may have been sent by malicious software, a browser plug-in, or a script that sends automated requests.  If you share your network connection, ask your administrator for help &mdash; a different computer using the same IP address may be responsible.  <a href="//support.google.com/websearch/answer/86640">Learn more</a><br><br>Sometimes you may be asked to solve the CAPTCHA if you are using advanced terms that robots are known to use, or sending requests very quickly.
    </div>




 IP address: 189.28.128.242<br>Time: 2016-06-27T14:52:27Z<br>URL: http://www.google.com/search?q=mkyong&amp;safe=active<br>
 </div>
</div>
</body>
</html>

希望它有所帮助！

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