生成随机端口函数

这个函数用来生成一个随机端口，可以生成一个没有被占用的端口。

//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;

}