C++实现软件自动更新功能

软件时常需要更新，如果通过在线通知用户肯定会更方便，实现原理也很简单，通过获取服务器文件中版本号与软件自身版本号对比，给出提示。下面把实现的代码(C++)贴出来，供大家参考。

0.用到的头文件

#include
#pragma comment(lib, "WS2_32")  // 链接到WS2_32.lib

1.启动Windows Sockets,初始化WS2_32.dll 

    WSADATA wsaData;
    WORD  sockVersion = MAKEWORD(2, 2);
    if  (::WSAStartup(sockVersion, &wsaData) != 0)
    {
        ::WSACleanup();
        return  FALSE;
    }

2. 通过"套接字"向网络发出请求或者应答网络请求.

    SOCKET sClient;
    int  ret;
    sClient = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
    if  (sClient == INVALID_SOCKET)
    {
        return  FALSE;
    }

3.设置发送和接收时间为超时8秒

    // set Recv and Send time out
    int  TimeOut = 8000;  // 设置发送超时8秒
    if  (setsockopt(sClient, SOL_SOCKET, SO_SNDTIMEO, ( char  *)&TimeOut,  sizeof (TimeOut)) == SOCKET_ERROR)
    {
        closesocket(sClient);
        return  FALSE;
    }


    if  (setsockopt(sClient, SOL_SOCKET, SO_RCVTIMEO, ( char  *)&TimeOut,  sizeof (TimeOut)) == SOCKET_ERROR)
    {
        closesocket(sClient);
        return  FALSE;
    }

4.获取与套接口相关的操作参数

    unsigned  long  ul = 1;
    ret = ioctlsocket(sClient, FIONBIO, (unsigned  long  *)&ul);
    if  (ret == SOCKET_ERROR)
    {
        closesocket(sClient);
        return  FALSE;
    }

5.sockaddr结构初始化，可通过设置服务器ip或网站地址。
gethostbyname()返回对应于给定主机名的包含主机名字和地址信息的hostent结构指针。结构的声明与gethostaddr()中一致。
inet_addr(const char* strptr)返回：若字符串有效则将字符串转换为32位二进制网络字节序的IPV4地址，否则为INADDR_NONE

    struct  sockaddr_in server;
    server.sin_family = AF_INET;
    server.sin_port = htons(80);
    struct  hostent *pURL = gethostbyname( "www.yanxin8.com" );
    //const char* ip = "115.28.9.132";
    //server.sin_addr.s_addr = inet_addr(ip);
    server.sin_addr.s_addr =  *((unsigned  long *)pURL->h_addr);
    if  (server.sin_addr.s_addr == INADDR_NONE)
    {
        closesocket(sClient);
        return  FALSE;
    }

6.与远程主机建立连接

  BOOL  bConnRe = FALSE;
    if  (connect(sClient, ( struct  sockaddr *)&server,  sizeof (server)) == -1)
    {
        struct  timeval timeout_val;
        fd_set set;
        FD_ZERO(&set);
        FD_SET(sClient, &set);
        timeout_val.tv_sec = 1;
        timeout_val.tv_usec = 0;
        if  (select(0, NULL, &set, NULL, &timeout_val) > 0)
        {
            bConnRe = TRUE;
        }
        else
            bConnRe = FALSE;
    }
    else
        bConnRe = TRUE;

    if  (!bConnRe)
    {
        closesocket(sClient);
        return  FALSE;
    }

7.等待接收时间协议返回的时间。学习了Winsock I/O模型之后，最好使用异步I/O，以便设置超时。  
  按照http协议，发送请求数据
  char *request = "GET /version.txt HTTP/1.0\r\nHost:www.xxx.com\r\nConnection: Close\r\n\r\n";
  GET这个是表示以什么方式请求，HTTP中还有很多其他的请求方式，常用的GET  POST
  version.txt，要获取的资源的名称，version.txt为网站服务器根目录下的文件
  HTTP/1.0表示http协议的版本
  Host:www.xxx.com，用来指定访问的主机。

   int  nRecv = 0;
    ///version.txt
    char  *request =  "GET /version.txt HTTP/1.0\r\nHost:www.xxx.com\r\nConnection: Close\r\n\r\n" ;
    ret = send(sClient, request,  strlen (request), 0);
    Sleep(300);

8.接收返回的数据，然后做解析。下面是返回的数据，可以看到最后一行为设定的软件版本。

HTTP/1.1 200 OK
Date: Wed, 29 Apr 2015 08:08:02 GMT
Server: Apache/2.4.10 (Unix) OpenSSL/1.0.1e-fips mod_fastcgi/2.4.6
Last-Modified: Tue, 28 Apr 2015 11:04:41 GMT
ETag: "10-514c6d4462440"
Accept-Ranges: bytes
Content-Length: 16
Connection: close
Content-Type: text/plain
noteCard=V1.0.2;

  char  buf[2000] = { 0 };
    nRecv = ::recv(sClient, buf, 2000, 0);
    if  (nRecv > 0){
        string str(buf);
        //strstr(buf, "noteCard=");
        int  pos1 = str.find( "noteCard=" );
        if  (pos1 != -1){
            pos1 += 9;
            int  pos2 = str.find( ";" , pos1);
            verstr = str.substr(pos1, pos2 - pos1);
            return  true ;
        }
    }

9.关闭socket

    closesocket(sClient);
    ::WSACleanup();
     return  FALSE;