C++ 簡單實現HTTP GET/POST 請求

HTTP(超文本傳輸協議)是一種客戶端與服務端的傳輸協議，最早用於瀏覽器和服務器之間的通信，後來因爲其使用靈活、方便等特點，廣泛用於客戶端與服務端的通信。文章將簡單介紹HTTP協議，同時以C++方式分別實現HTTP GET、POST 請求

HTTP 請求報文

HTTP請求報文的一般格式由4部分組成：請求行、請求頭部、空行、請求數據。如下圖所示：

 

1.jpg

請求行：包含3部分內容：請求方法，URL，協議版本。形式如：GET /?aaa=1 HTTP/1.1。請求方法有GET、POST、HEAD、PUT、DELETE、OPTIONS等。URL指請求服務端的地址，可以是相對地址或域名形式的絕對地址。協議版本主要有HTTP/1.1 HTTP/1.0 HTTP/0.9，後面兩種已很少使用了。

請求頭部：以key/value形式成對錶示頭部參數，以英文冒號分隔。key名稱的約定寫法爲Key，Key-Name，自定義key名稱一般以“X-”開頭。如php的聲明“X-Powered-By:PHP/5.5.4-1”

空行：用來標識請求頭部的數據已結束。

請求數據：可選項，這塊內容只在POST方式下使用，作爲POST的數據表示區域。使用這塊內容，要在請求頭部以Content-Length聲明請求數據長度，以Content-Type聲明請求數據類型。

HTTP POST請求

HTTP POST方式是把請求參數放到HTTP請求報文的請求數據中，爲了讓例子更容易看懂，僅保留HTTP Post關鍵參數，你還可以自定義一些參數，比如瀏覽器喜歡用的User-Agent，Accept，Connection等等

char *pHttpPost = "POST %s HTTP/1.1\r\n"
    "Host: %s:%d\r\n"
    "Content-Type: application/x-www-form-urlencoded\r\n"
    "Content-Length: %d\r\n\r\n"
    "%s";
 
char* addr = "http://localhost/post.php";
char* host = "127.0.0.1";
int port = 80;
char* msg = "aaa=1&bbb=2";
 
char strHttpPost[1024] = {0};
sprintf(strHttpPost, pHttpPost, addr, host, port, strlen(msg), msg);
 
//這裏忽略掉了socket連接代碼
 
send(sockClient, strHttpPost, strlen(strHttpPost), 0);

HTTP GET請求

HTTP GET方式是把請求參數放到HTTP請求報文的請求行URL中，所以請求行就是“GET /?aaa=1&bbb=2 HTTP/1.1\r\n”。URL最大長度通常瀏覽器取255，這和文件路徑最大長度有關。雖然HTTP允許更大長度，但不建議怎麼做，如果太長了，可以考慮換成POST方式

char *pHttpGet = "GET %s?%s HTTP/1.1\r\n"
    "Host: %s:%d\r\n\r\n";
 
char* addr = "http://localhost/get.php";
char* host = "127.0.0.1";
int post = 80;
char* msg = "aaa=1&bbb=2";
 
char strHttpGet[1024] = {0};
sprintf(strHttpGet, pHttpGet, addr, msg,  host, post);
 
//這裏忽略掉了socket連接代碼
 
send(sockClient, strHttpGet, strlen(strHttpGet), 0);

實現的HTTP

#include "HttpConnect.h"
 
#ifdef WIN32
#pragma comment(lib,"ws2_32.lib")
#endif
HttpConnect::HttpConnect()
{
#ifdef WIN32
    //此處一定要初始化一下，否則gethostbyname返回一直爲空
    WSADATA wsa = { 0 };
    WSAStartup(MAKEWORD(2, 2), &wsa);
#endif
}
HttpConnect::~HttpConnect()
{
}
void HttpConnect::socketHttp(std::string host, std::string request)
{
    int sockfd;
    struct sockaddr_in address;
    struct hostent *server;
    sockfd = socket(AF_INET,SOCK_STREAM,0);
    address.sin_family = AF_INET;
    address.sin_port = htons(80);
    server = gethostbyname(host.c_str());
    memcpy((char *)&address.sin_addr.s_addr,(char*)server->h_addr, server->h_length);
    if(-1 == connect(sockfd,(struct sockaddr *)&address,sizeof(address))){
        DBG <<"connection error!"<<std::endl;
        return;
    }
    DBG << request << std::endl;
#ifdef WIN32
    send(sockfd, request.c_str(),request.size(),0);
#else
    write(sockfd,request.c_str(),request.size());
#endif
    char buf[1024*1024] = {0};
    int offset = 0;
    int rc;
#ifdef WIN32
    while(rc = recv(sockfd, buf+offset, 1024,0))
#else
    while(rc = read(sockfd, buf+offset, 1024))
#endif
    {
        offset += rc;
    }
#ifdef WIN32
    closesocket(sockfd);
#else
    close(sockfd);
#endif
    buf[offset] = 0;
    DBG << buf << std::endl;
}
void HttpConnect::postData(std::string host, std::string path, std::string post_content)
{
    //POST請求方式
    std::stringstream stream;
    stream << "POST " << path;
    stream << " HTTP/1.0\r\n";
    stream << "Host: "<< host << "\r\n";
    stream << "User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.1; zh-CN; rv:1.9.2.3) Gecko/20100401 Firefox/3.6.3\r\n";
    stream << "Content-Type:application/x-www-form-urlencoded\r\n";
    stream << "Content-Length:" << post_content.length()<<"\r\n";
    stream << "Connection:close\r\n\r\n";
    stream << post_content.c_str();
    socketHttp(host, stream.str());
}
void HttpConnect::getData(std::string host, std::string path, std::string get_content)
{
    //GET請求方式
    std::stringstream stream;
    stream << "GET " << path << "?" << get_content;
    stream << " HTTP/1.0\r\n";
    stream << "Host: " << host << "\r\n";
    stream <<"User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.1; zh-CN; rv:1.9.2.3) Gecko/20100401 Firefox/3.6.3\r\n";
    stream <<"Connection:close\r\n\r\n";
    socketHttp(host, stream.str());
}

    HttpConnect *http = new HttpConnect();
    http->getData("127.0.0.1", "/login", "id=liukang&pw=123");
    http->postData("127.0.0.1", "/login","id=liukang&pw=123");