UDP

UDP数据传输

非面向连接,不安全,数据可能丢失,效率高

1.例:传输一个字符串

服务器端

public void sever() throws Exception{
		//1.创建服务端及端口
		DatagramSocket server=new DatagramSocket(8888);
		//2.准备接受容器 byte数组
		byte[] container=new byte[1024];
		//3.将接受容器打包
		DatagramPacket packet=new DatagramPacket(container, container.length);
		//4.接收数据
		server.receive(packet);
		//5.分析数据
		byte[] data=packet.getData();
		int len=packet.getLength();
		System.out.println(new String(data,0,len));
		//6.释放资源
		server.close();
	}

客户端

public void client() throws Exception{
		//1.创建客户端及端口
		DatagramSocket client=new DatagramSocket(7777);
		//2.准备数据
		String sdata=new String("你好");
		byte[] data=sdata.getBytes();
		//3.打包数据
		DatagramPacket packet=new DatagramPacket(data, data.length ,new InetSocketAddress("localhost", 8888));
		//4.发送
		client.send(packet);
		//5.释放
		client.close();
	}

2.例:传输一个double数据

@Test
	public void testClient() throws IOException {
		DatagramSocket client=new DatagramSocket(7777);
		double d=1.1;
		byte[] data=convert(d);
		DatagramPacket pack=new DatagramPacket(data, data.length,new InetSocketAddress("localhost",8888));
		client.send(pack);
		client.close();
	}
	/*
	 * 将double类型转化为字节数组:
	 * 用数据输出流将double输出到字节数组输出流中
	 * 再将字节数组输出流转化为字节数组
	 */
	public byte[] convert(double b) throws IOException {
		byte[] data;
		//写到流中----->选择输出流
		ByteArrayOutputStream bos=new ByteArrayOutputStream();
		DataOutputStream dos=new DataOutputStream(bos);
		dos.writeDouble(b);
		dos.flush();
		
		data=bos.toByteArray();
		
		dos.close();
		
		return data;
		
	}
	
	@Test
	public void testServer() throws IOException {
		DatagramSocket server=new DatagramSocket(8888);
		byte[] data=new byte[1024];
		DatagramPacket pack=new DatagramPacket(data, 1024);
		server.receive(pack);
		double d=convert(pack.getData());
		System.out.println(d);
	}
	/*
	 * 将字节数组---->double:
	 * 用字节数组初始化字节数组输入流
	 * 用数据输入流包裹字节数组输入流
	 * 从数据输入流中读出double
	 */
	public double convert(byte[] data) throws IOException {
		double b;
		//从流中读出来----->选择输入流
		DataInputStream in=new DataInputStream(new ByteArrayInputStream(data));
		b=in.readDouble();
		return b;
	}

*若服务器端没建好,直接运行客户端也不会报错.因为UDP是非面向连接的