windows下设置socket的connect超时

变相的实现connect的超时，我要讲的就是这个方法，原理上是这样的：
1．建立socket
2．将该socket设置为非阻塞模式
3．调用connect()
4．使用select()检查该socket描述符是否可写（注意，是可写）
5．根据select()返回的结果判断connect()结果
6．将socket设置为阻塞模式（如果你的程序不需要用阻塞模式的，这步就省了，不过一般情况下都是用阻塞模式的，这样也容易管理）

 

// widonws: 默认设置socket TCP client connect为阻塞模式
void TcpConnect(char* strIP, UINT nPort)
{
    struct sockaddr_in serverAddress;
    SOCKET hSocket = NULL;

    hSocket = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
    if( hSocket==INVALID_SOCKET)
    {
        return;
    }

    memset(&serverAddress, 0, sizeof(serverAddress));     
    serverAddress.sin_family      = AF_INET;
    serverAddress.sin_addr.s_addr = inet_addr(strIP);   
    serverAddress.sin_port        = htons((short)nPort);      
    int iTimeOut = 3000;
    setsockopt(hSocket,SOL_SOCKET,SO_RCVTIMEO,(char*)&iTimeOut,sizeof(iTimeOut));
    setsockopt(hSocket,SOL_SOCKET,SO_SNDTIMEO,(char*)&iTimeOut,sizeof(iTimeOut));    

    if( SOCKET_ERROR==connect(hSocket, (sockaddr*)&serverAddress, sizeof(serverAddress)) )
    {        
        closesocket(hSocket);
        DWORD gle = WSAGetLastError();

        return;
    }

    char buff[] = "hello";
    int sl=::send(hSocket,(char*)buff, sizeof(buff), 0);
    if( sl<0 )
    {
        closesocket(hSocket);
        return ;
    }
    closesocket(hSocket);
}

// widonws: 设置socket TCP client connect非阻塞模式
void SockSelect(char* strIP, UINT nPort)
{
    SOCKET/*int*/ sockfd = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
    if(sockfd < 0) 
    {
        return;
    }
    struct sockaddr_in serv_addr;

    //以服务器地址填充结构serv_addr
    serv_addr.sin_family = AF_INET;
    serv_addr.sin_addr.s_addr = inet_addr(strIP);
    serv_addr.sin_port = htons(nPort);
    int error = -1;
    int len = sizeof(int);
    timeval tm;
    fd_set set;
    unsigned long ul = 1;
    ioctlsocket(sockfd, FIONBIO, &ul); //设置为非阻塞模式
    bool ret = false;
    if( connect(sockfd, (struct sockaddr *)&serv_addr, sizeof(serv_addr)) == -1)
    {
        tm.tv_sec  = 3;
        tm.tv_usec = 0;
        FD_ZERO(&set);
        FD_SET(sockfd, &set);
        if( select(sockfd+1, NULL, &set, NULL, &tm) > 0)
        {
            getsockopt(sockfd, SOL_SOCKET, SO_ERROR, (char *)&error, /*(socklen_t *)*/&len);
            if(error == 0) 
                ret = true;
            else 
                ret = false;
        } 
        else 
            ret = false;
    }
    else 
        ret = true;
    ul = 0;
    ioctlsocket(sockfd, FIONBIO, &ul); //设置为阻塞模式
    if(!ret) 
    {
        closesocket( sockfd );
        fprintf(stderr , "Cannot Connect the server!/n");
        return;
    }

    fprintf( stderr , "Connected!/n");

    char buff[] = "hello";
    int sl=::send(sockfd,(char*)buff, sizeof(buff), 0);

    closesocket( sockfd );
}