C/C++语言Http请求获取数据

    工作一个星期了，基本都在看别人代码。现在主要看的是Http部分的，不断和服务器交互，不断得到反馈信息或者提交信息。诸如此类，因此为了加深C对Http的处理，还是稍微练习下或者说了解和实验下，俗话说“好记性不如烂笔头”，厉害的人都是靠学习来的。

   在Windows下利用C语言进行http请求，向google天气API发送请求获取数据并保存!以下是工程文件：

各个文件代码：

//> downdata.h

#ifndef DOWNDATA_H_INCLUDED
#define DOWNDATA_H_INCLUDED

#define BUFFSIZE_H 1024

#ifdef __cpluscplus
extern "C"
{
#endif

/**
* @brief 向网络请求资源，返回值存储到当前目录的临时文件whether.txt中.
* @param pUrl[in] - 请求的URL.
* @return if get data return true, else if get nothing return false.
*/
bool WEBQuest(const char * pUrl);

#ifdef __cpluscplus
}
#endif

#endif // DOWNDATA_H_INCLUDED

//> downdata.cpp

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
//#include "windows.h"
#include "winsock2.h"

#include "downdata.h"
#include "freeptr.h"

#pragma comment(lib, "ws2_32.lib") //在某些编译器下，需要添加编译参数到工程设置中，比如CodeBlocks(这样，这行就不需要了).
                                                                      //Code::blocks 中新建一个工程， 然后右击工程
                                                                      //选择 build options -> Linker setting
                                                                      //在Other linker options 中添加： -lwsock32
/**
* @brief 为了加深http的理解和数据相关的操作，实现之.
*/
bool WEBQuest(const char * pUrl)
{
#if 1 //no this declaration, socket create failed.
    WSADATA WsaData;

    if (WSAStartup(MAKEWORD(2,2),&WsaData))
    {
        printf("The socket failed");
        return false;
    }
#endif

    SOCKET sockeId;
    SOCKADDR_IN addr;

    if (-1 == (sockeId = socket(AF_INET, SOCK_STREAM, 0)))
    {
        printf("socket create failed\n");
        return false;
    }

    /// < dest_addr
    addr.sin_addr.S_un.S_addr = inet_addr("74.125.71.105"); /// < googleIP，可以用IP地址查询得到
    addr.sin_family = AF_INET;
    addr.sin_port = htons(80);

    /// < 分离url中的主机地址和相对路径 考虑到内存和性能，下面不是好习惯！
    char *phost = 0;
    char * myurl = (char * ) malloc (BUFFSIZE_H * sizeof(char));
    char * host = (char * ) malloc (BUFFSIZE_H * sizeof(char));
    char * GET = (char * ) malloc (BUFFSIZE_H * sizeof(char));
    char * head =(char * ) malloc(BUFFSIZE_H * sizeof(char));
    memset(myurl, '\0', BUFFSIZE_H);
    memset(host, '\0', BUFFSIZE_H);
    memset(GET, '\0', BUFFSIZE_H);
    memset(head, '\0', BUFFSIZE_H);

    /// < pUrl - www.google.com/ig/api?hl=zh_cn&weather=beijing
    /// < www.google.com - &host
    /// < /ig/api?hl=zh_cn&weather=beijing - &GET
    strcpy(myurl, pUrl);

    for (phost = myurl; *phost != '/' && *phost != '\0'; ++phost);
    if ( (int)(phost - myurl) == strlen(myurl) )
        strcpy(GET, "/");
    else
        strcpy(GET, phost);
    *phost = '\0'; /// < 相当于在www.google.com/的/位置替换为'\0'.
    strcpy(host, myurl); /// < 在www.google.com/的/位置为'\0'，因此www.google.com被拷贝到&host.
    printf("%s\n%s\n", host, GET);

    /**
    * 组织发送到web服务器的信息
    * 为何要发送下面的信息connect请参考HTTP协议的约定
    */
    strcat(head, "GET ");
    strcat(head, GET);
    strcat(head, " HTTP/1.1\r\n");
    strcat(head, "host: ");
    strcat(head, host);
    strcat(head, "\r\nConnection: Close\r\n\r\n");
    printf(head);

    if (SOCKET_ERROR == connect(sockeId, (SOCKADDR * )&addr, sizeof(addr)))
    {
        printf("connect failed!\n");
        closesocket(sockeId);
        WSACleanup();
#if 0
        free(myurl);
        free(host);
        free(GET);
        free(head);
        myurl = NULL;
        host = NULL;
        GET = NULL;
        head = NULL;
#endif
        freeCharPtr(&myurl, &host, &GET, &head, NULL);

        return false;
    }

    if (SOCKET_ERROR == send(sockeId, head, strlen(head), 0))
    {
        printf("send &header error!\n");
        closesocket(sockeId);
        WSACleanup();
#if 0
        free(myurl);
        free(host);
        free(GET);
        free(head);
        myurl = NULL;
        host = NULL;
        GET = NULL;
        head = NULL;
#endif
          freeCharPtr(&myurl, &host, &GET, &head, NULL);

        return false;
    }

    memset(head, '\0', BUFFSIZE_H);
    FILE *fp;
    fp = fopen("whether.xml", "w+");
    if (NULL == fp)
    {
        printf("whether file create failed!\n");
        closesocket(sockeId);
        WSACleanup();
#if 0
        free(myurl);
        free(host);
        free(GET);
        free(head);
        myurl = NULL;
        host = NULL;
        GET = NULL;
        head = NULL;
#endif
        freeCharPtr(&myurl, &host, &GET, &head, NULL);

        return false;
    }
    while (recv(sockeId, head, BUFFSIZE_H, 0) > 0)
    {
        fputs(head, fp);
        memset(head, '\0', BUFFSIZE_H);
    }
#if 0
    free(myurl);
    free(host);
    free(GET);
    free(head);
    myurl = NULL;
    host = NULL;
    GET = NULL;
    head = NULL;
#endif
    freeCharPtr(&myurl, &host, &GET, &head, NULL);
    closesocket(sockeId);
    WSACleanup();

    return true;
}

/// < main.cpp
#include <iostream> /// < system()
#include <stdio.h>
#include "downdata.h"
using namespace std;

int main(void )
{
    if (!WEBQuest("" ))
    {
        return -1;
    }
    printf( "Whether have been writtend to file whether.xml\n" );

    system( "pause");
    return 0;
}

//> 关于内存释放，自己封装了一个变参形式的(char **参数)释放函数
//> freeptr.h

#ifndef FREEPTR_H
#define FREEPTR_H

#ifdef __cpluscplus
extern "C"
{
#endif

/**
* @brief 变参形式内存释放
* param[in] ch - 字符指针
* param[in] ... - 其他字符指针
* 接口使用规范：
*
*/
void freeCharPtr(char ** ch, ...);

#ifdef __cpluscplus
}
#endif
#endif

//> freeptr.cpp

#include <stdlib.h>
#include <stdarg.h>
#include "freeptr.h"

/**
* @brief 变参形式内存释放
*/
void freeCharPtr(char ** ch, ...)
{
          va_list ap;
          char ** p;

          va_start(ap, ch);
          free(*ch);
          *ch = NULL;
          while (p = va_arg(ap, char ** ))
          {
                  free(*p);
                  *p = NULL;
          }
}