C 使用libcurl做HttpClient - 《libcurl》

当使用C++做HTTP客户端时，目前通用的做法就是使用libcurl。其官方网站的地址是http://curl.haxx.se/，该网站主要提供了Curl和libcurl。Curl是命令行工具，用于完成FTP, FTPS, HTTP, HTTPS, GOPHER, TELNET, DICT, FILE 以及 LDAP的命令的请求及接收回馈。libcurl提供给开发者，用于使用C++跨平台的开发各种网络协议的请求及响应。里面的文档非常齐全，不过都是英文的。

本文提供最简单的demo使用libcurl开发HttpClient。主要包括同步的HTTP GET、HTTP POST、HTTPS GET、HTTPS POST。

下载libcurl包，如果使用Linux平台，建议下载源文件编译；如果使用Windows平台，建议下载Win32 - MSVC，下载地址是：http://curl.haxx.se/download.html

#ifndef __HTTP_CURL_H__  
#define __HTTP_CURL_H__  
#include <string>  
class CHttpClient  
{  
public:  
    CHttpClient(void);  
    ~CHttpClient(void);  
public:  
    /** 
    * @brief HTTP POST请求 
    * @param strUrl 输入参数,请求的Url地址,如:http://www.baidu.com 
    * @param strPost 输入参数,使用如下格式para1=val1¶2=val2&… 
    * @param strResponse 输出参数,返回的内容 
    * @return 返回是否Post成功 
    */  
    int Post(const std::string & strUrl, const std::string & strPost, std::string & strResponse);  
    /** 
    * @brief HTTP GET请求 
    * @param strUrl 输入参数,请求的Url地址,如:http://www.baidu.com 
    * @param strResponse 输出参数,返回的内容 
    * @return 返回是否Post成功 
    */  
    int Get(const std::string & strUrl, std::string & strResponse);  
    /** 
    * @brief HTTPS POST请求,无证书版本 
    * @param strUrl 输入参数,请求的Url地址,如:https://www.alipay.com 
    * @param strPost 输入参数,使用如下格式para1=val1¶2=val2&… 
    * @param strResponse 输出参数,返回的内容 
    * @param pCaPath 输入参数,为CA证书的路径.如果输入为NULL,则不验证服务器端证书的有效性. 
    * @return 返回是否Post成功 
    */  
    int Posts(const std::string & strUrl, const std::string & strPost, std::string & strResponse, const char * pCaPath = NULL);  
    /** 
    * @brief HTTPS GET请求,无证书版本 
    * @param strUrl 输入参数,请求的Url地址,如:https://www.alipay.com 
    * @param strResponse 输出参数,返回的内容 
    * @param pCaPath 输入参数,为CA证书的路径.如果输入为NULL,则不验证服务器端证书的有效性. 
    * @return 返回是否Post成功 
    */  
    int Gets(const std::string & strUrl, std::string & strResponse, const char * pCaPath = NULL);  
public:  
    void SetDebug(bool bDebug);  
private:  
    bool m_bDebug;  
};  
#endif

#include "httpclient.h"  
#include "curl/curl.h"  
#include <string>  
CHttpClient::CHttpClient(void) :   
m_bDebug(false)  
{  
}  
CHttpClient::~CHttpClient(void)  
{  
}  
static int OnDebug(CURL *, curl_infotype itype, char * pData, size_t size, void *)  
{  
    if(itype == CURLINFO_TEXT)  
    {  
        //printf("[TEXT]%s\n", pData);  
    }  
    else if(itype == CURLINFO_HEADER_IN)  
    {  
        printf("[HEADER_IN]%s\n", pData);  
    }  
    else if(itype == CURLINFO_HEADER_OUT)  
    {  
        printf("[HEADER_OUT]%s\n", pData);  
    }  
    else if(itype == CURLINFO_DATA_IN)  
    {  
        printf("[DATA_IN]%s\n", pData);  
    }  
    else if(itype == CURLINFO_DATA_OUT)  
    {  
        printf("[DATA_OUT]%s\n", pData);  
    }  
    return 0;  
}  
static size_t OnWriteData(void* buffer, size_t size, size_t nmemb, void* lpVoid)  
{  
    std::string* str = dynamic_cast<std::string*>((std::string *)lpVoid);  
    if( NULL == str || NULL == buffer )  
    {  
        return -1;  
    }  
    char* pData = (char*)buffer;  
    str->append(pData, size * nmemb);  
    return nmemb;  
}  
int CHttpClient::Post(const std::string & strUrl, const std::string & strPost, std::string & strResponse)  
{  
    CURLcode res;  
    CURL* curl = curl_easy_init();  
    if(NULL == curl)  
    {  
        return CURLE_FAILED_INIT;  
    }  
    if(m_bDebug)  
    {  
        curl_easy_setopt(curl, CURLOPT_VERBOSE, 1);  
        curl_easy_setopt(curl, CURLOPT_DEBUGFUNCTION, OnDebug);  
    }  
    curl_easy_setopt(curl, CURLOPT_URL, strUrl.c_str());  
    curl_easy_setopt(curl, CURLOPT_POST, 1);  
    curl_easy_setopt(curl, CURLOPT_POSTFIELDS, strPost.c_str());  
    curl_easy_setopt(curl, CURLOPT_READFUNCTION, NULL);  
    curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, OnWriteData);  
    curl_easy_setopt(curl, CURLOPT_WRITEDATA, (void *)&strResponse);  
    curl_easy_setopt(curl, CURLOPT_NOSIGNAL, 1);  
    curl_easy_setopt(curl, CURLOPT_CONNECTTIMEOUT, 3);  
    curl_easy_setopt(curl, CURLOPT_TIMEOUT, 3);  
    res = curl_easy_perform(curl);  
    curl_easy_cleanup(curl);  
    return res;  
}  
int CHttpClient::Get(const std::string & strUrl, std::string & strResponse)  
{  
    CURLcode res;  
    CURL* curl = curl_easy_init();  
    if(NULL == curl)  
    {  
        return CURLE_FAILED_INIT;  
    }  
    if(m_bDebug)  
    {  
        curl_easy_setopt(curl, CURLOPT_VERBOSE, 1);  
        curl_easy_setopt(curl, CURLOPT_DEBUGFUNCTION, OnDebug);  
    }  
<pre name="code" class="cpp">   curl_easy_setopt(curl, CURLOPT_URL, strUrl.c_str());  
    curl_easy_setopt(curl, CURLOPT_READFUNCTION, NULL);  
    curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, OnWriteData);  
    curl_easy_setopt(curl, CURLOPT_WRITEDATA, (void *)&strResponse);  
    /** 
    * 当多个线程都使用超时处理的时候，同时主线程中有sleep或是wait等操作。 
    * 如果不设置这个选项，libcurl将会发信号打断这个wait从而导致程序退出。 
    */  
    curl_easy_setopt(curl, CURLOPT_NOSIGNAL, 1);  
    curl_easy_setopt(curl, CURLOPT_CONNECTTIMEOUT, 3);  
    curl_easy_setopt(curl, CURLOPT_TIMEOUT, 3);  
    res = curl_easy_perform(curl);  
    curl_easy_cleanup(curl);  
    return res;  
}  
int CHttpClient::Posts(const std::string & strUrl, const std::string & strPost, std::string & strResponse, const char * pCaPath)  
{  
    CURLcode res;  
    CURL* curl = curl_easy_init();  
    if(NULL == curl)  
    {  
        return CURLE_FAILED_INIT;  
    }  
    if(m_bDebug)  
    {  
        curl_easy_setopt(curl, CURLOPT_VERBOSE, 1);  
        curl_easy_setopt(curl, CURLOPT_DEBUGFUNCTION, OnDebug);  
    }  
    curl_easy_setopt(curl, CURLOPT_URL, strUrl.c_str());  
    curl_easy_setopt(curl, CURLOPT_POST, 1);  
    curl_easy_setopt(curl, CURLOPT_POSTFIELDS, strPost.c_str());  
    curl_easy_setopt(curl, CURLOPT_READFUNCTION, NULL);  
    curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, OnWriteData);  
    curl_easy_setopt(curl, CURLOPT_WRITEDATA, (void *)&strResponse);  
    curl_easy_setopt(curl, CURLOPT_NOSIGNAL, 1);  
    if(NULL == pCaPath)  
    {  
        curl_easy_setopt(curl, CURLOPT_SSL_VERIFYPEER, false);  
        curl_easy_setopt(curl, CURLOPT_SSL_VERIFYHOST, false);  
    }  
    else  
    {  
        //缺省情况就是PEM，所以无需设置，另外支持DER  
        //curl_easy_setopt(curl,CURLOPT_SSLCERTTYPE,"PEM");  
        curl_easy_setopt(curl, CURLOPT_SSL_VERIFYPEER, true);  
        curl_easy_setopt(curl, CURLOPT_CAINFO, pCaPath);  
    }  
    curl_easy_setopt(curl, CURLOPT_CONNECTTIMEOUT, 3);  
    curl_easy_setopt(curl, CURLOPT_TIMEOUT, 3);  
    res = curl_easy_perform(curl);  
    curl_easy_cleanup(curl);  
    return res;  
}  
int CHttpClient::Gets(const std::string & strUrl, std::string & strResponse, const char * pCaPath)  
{  
    CURLcode res;  
    CURL* curl = curl_easy_init();  
    if(NULL == curl)  
    {  
        return CURLE_FAILED_INIT;  
    }  
    if(m_bDebug)  
    {  
        curl_easy_setopt(curl, CURLOPT_VERBOSE, 1);  
        curl_easy_setopt(curl, CURLOPT_DEBUGFUNCTION, OnDebug);  
    }  
    curl_easy_setopt(curl, CURLOPT_URL, strUrl.c_str());  
    curl_easy_setopt(curl, CURLOPT_READFUNCTION, NULL);  
    curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, OnWriteData);  
    curl_easy_setopt(curl, CURLOPT_WRITEDATA, (void *)&strResponse);  
    curl_easy_setopt(curl, CURLOPT_NOSIGNAL, 1);  
    if(NULL == pCaPath)  
    {  
        curl_easy_setopt(curl, CURLOPT_SSL_VERIFYPEER, false);  
        curl_easy_setopt(curl, CURLOPT_SSL_VERIFYHOST, false);  
    }  
    else  
    {  
        curl_easy_setopt(curl, CURLOPT_SSL_VERIFYPEER, true);  
        curl_easy_setopt(curl, CURLOPT_CAINFO, pCaPath);  
    }  
    curl_easy_setopt(curl, CURLOPT_CONNECTTIMEOUT, 3);  
    curl_easy_setopt(curl, CURLOPT_TIMEOUT, 3);  
    res = curl_easy_perform(curl);  
    curl_easy_cleanup(curl);  
    return res;  
}  
///////////////////////////////////////////////////////////////////////////////////////////////  
void CHttpClient::SetDebug(bool bDebug)  
{  
    m_bDebug = bDebug;  
}