生成随机端口函数

//生成随机端口
DWORD GenerateRandomPort()
{
        int nStartPort = 1000;
        int nEndPort = 10000;
        FD_SET fd_Write;
        SOCKET s;
        struct sockaddr_in server;
        struct timeval tp = { 0 };
        int ret = 0;
        unsigned long mode = 1; 
        tp.tv_sec = 0;  
        tp.tv_usec = 50; 
        FD_ZERO(&fd_Write);  
        server.sin_family = AF_INET;
        server.sin_addr.s_addr = inet_addr("127.0.0.1");
        for(nStartPort; nStartPort != nEndPort; ++nStartPort)
        {
                s=socket(AF_INET,SOCK_STREAM, IPPROTO_TCP);
                FD_SET(s, &fd_Write);
                ioctlsocket(s, FIONBIO, &mode); 
                server.sin_port=htons(nStartPort);
                connect(s,(struct sockaddr *)&server,sizeof(server));
                ret=select(0, NULL, &fd_Write, NULL, &tp);  
                if(0 == ret || -1 == ret)
                {
                        closesocket(s);
                        WSACleanup();
                        return nStartPort;
                }
                closesocket(s);
        }
        WSACleanup();
        return nStartPort;
}