走进http的世界------用C代码模拟浏览器IE(http client)访问web(http server)的行为

浏览数：28 / 时间：2015年06月09日

在本文中，我们来玩一下http. 既然你看到了这篇文章，那就说明你肯定直接或间接借助了http协议（浏览器的实现需要用到http协议）。很多书本把http介绍得玄乎其玄，高深莫测，其实， http也没什么大不了的。

当我们用浏览器看登录www.baidu.com的时候，浏览器相当于客户端，而服务端是百度公司掌控着。要想大致了解http, 网上资料可谓如山如海。作为一名程序员（注意，我说的是程序猿），我始终坚信，没有代码，没有实践，只讲理论，那就是扯淡，尽管一些人乐此不疲。

上面说了，百度公司掌握着百度服务器，在百度公司工作的那些程序猿等员工早就把服务端的程序和资料做好了，所以这次我们就不用写服务端程序了，我们只需要管客户端(http client)即可。在这里，我们说http client, 实际也是tcp client, 但由于tcp传送的是http协议格式的信息(以html语言形式存在)，所以，把此处的把tcp client叫为http client, 这样，可以更好地“装B”.

好吧，我们来用C代码模拟浏览器IE(http client)访问web(http server)的行为。（请注意，如果需要了解http的一些基本知识，请在网上自己找资料学一下，到处都是）

废话说多了，直接看http client(tcp client)的代码：（请注意：一定要确保你的pc能ping通www.baidu.com）

// 用C代码模拟浏览器IE(http client)访问web(http server)的行为

#include <stdio.h>
#include <winsock2.h>
#pragma comment(lib, "ws2_32.lib")

int main()
{
	// 网络初始化
    WSADATA wsaData;
    WSAStartup(MAKEWORD(1,1), &wsaData);

	// 我们来访问一下度娘
	char szWeb[] = "www.baidu.com"; // !!!强调: 你的pc一定要能ping通www.baidu.com, 否则程序不能正常运行就不要找我啦
    HOSTENT *pHost = gethostbyname(szWeb);
    
	// 度娘的ip地址
	const char* pIPAddr = inet_ntoa(*((struct in_addr *)pHost->h_addr)) ;
    printf("web server ip is : %s\n", pIPAddr);

	// 度娘服务器信息
    SOCKADDR_IN  webServerAddr;
    webServerAddr.sin_family = AF_INET;
    webServerAddr.sin_addr.S_un.S_addr=inet_addr(pIPAddr);
    webServerAddr.sin_port = htons(80);
 
	// 创建客户端通信socket
    SOCKET sockClient = socket(AF_INET, SOCK_STREAM, 0);

	// 去连接度娘
    int nRet = connect(sockClient ,(struct sockaddr*)&webServerAddr, sizeof(webServerAddr));
    if(nRet < 0)
	{
		printf("connect error\n");
		return 1;
	}

	// 准备向度娘发送http的GET请求
    char szHttpRest[1024] = {0};
	sprintf(szHttpRest, "GET /index.html HTTP/1.1\nHost:%s\r\nConnection: Keep-Alive\r\n\r\n", szWeb);
    printf("\n---------------------send is :---------------------\n");
	printf("%s\n", szHttpRest);
 
	// 利用tcp向度娘发送http的GET请求
    nRet = send(sockClient , szHttpRest, strlen(szHttpRest) + 1, 0);
	if(nRet < 0)
	{
		printf("send error\n");
		return 1;
	}

	// 把度娘返回的信息保存在文件test.txt中
	FILE *fp = fopen("test.txt", "w");
	while(1)
	{
			// 每次接收一个字节
		    char szRecvBuf[2] = {0};
			nRet = recv(sockClient ,szRecvBuf, 1 ,0);
			
			// 接收错误
			if(nRet < 0)
			{
				printf("recv error\n");
				goto LABEL;
			}			
			
			// 度娘主动断开了连接
			if(0 == nRet)
			{
				printf("connection has beed closed by web server\n");
				goto LABEL;
			}
			
			static int flag = 0;
			if(0 == flag)
			{
				printf("writing data to file\n");
				flag = 1;
			}

			// 把度娘返回的信息写入文件
			fputc(szRecvBuf[0], fp);
	}


LABEL: // 这个单词不要写错啦， 很多童鞋容易写错
	fclose(fp);
	closesocket(sockClient);  
    WSACleanup();  

    return nRet < 0 ? 1 : 0;
}

好，运行它。我们看看控制台上的结果：

web server ip is : 180.97.33.108 （请注意，你运行上面程序，此处可能得到不同的ip, 不过没关系的，不要管这个。）

---------------------send is :---------------------
GET /index.html HTTP/1.1
Host:www.baidu.com
Connection: Keep-Alive

writing data to file
connection has beed closed by web server

激动人心的时刻即将来临，我们来看看test.txt里面的内容吧：

TTP/1.1 200 OK

Date: Wed, 15 Apr 2015 14:46:54 GMT

Content-Type: text/html

Content-Length: 14613

Last-Modified: Wed, 03 Sep 2014 02:48:32 GMT

Connection: Keep-Alive

Vary: Accept-Encoding

Set-Cookie: BAIDUID=BA3F027F25DD29D6475B7245AD24D192:FG=1; expires=Thu, 31-Dec-37 23:55:55 GMT; max-age=2147483647; path=/; domain=.baidu.com

Set-Cookie: BIDUPSID=BA3F027F25DD29D6475B7245AD24D192; expires=Thu, 31-Dec-37 23:55:55 GMT; max-age=2147483647; path=/; domain=.baidu.com

Set-Cookie: BDSVRTM=0; path=/

P3P: CP=" OTI DSP COR IVA OUR IND COM "

Server: BWS/1.1

Pragma: no-cache

Cache-control: no-cache

BDPAGETYPE: 1

BDQID: 0xc17b13c300000a74

BDUSERID: 0

Accept-Ranges: bytes

<!DOCTYPE html>

<html>

<head>

<meta http-equiv="content-type" content="text/html;charset=utf-8">

<meta http-equiv="X-UA-Compatible" content="IE=Edge">

<link rel="dns-prefetch" href="//s1.bdstatic.com"/>

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