网络Socket编程UDP协议例子

服务端代码

public class UDPChatServer {
    //通讯端口
    private Integer port=8000;
    //数据报文的通讯通道对象
    private DatagramChannel channel;
    //发送数据的最大大小
    private final Integer MAX_SIZE=1024;
    
    private Charset charset=Charset.forName("UTF-8");

    public UDPChatServer() throws IOException {
        //DatagramChannel本身的open方法返回一个DatagramChannel对象
        channel=DatagramChannel.open();
        //获取数据报的socket对象UDP 的socket
        DatagramSocket socket=channel.socket();
        //将socket对象绑定上本地的端口
        SocketAddress address=new InetSocketAddress(port);
        socket.bind(address);
        System.out.println("server started!");
    }
    private void service(){
        //初始化一个新的字节缓存对象容量为MAX_SIZE=1024 个字节。
        ByteBuffer receiveBuffer=ByteBuffer.allocate(MAX_SIZE);
        while (true){
              //将缓存中的数据清空
            receiveBuffer.clear();
            try {
                //从渠道中获取固定大小的数据，获取client连接
               InetSocketAddress client= (InetSocketAddress) channel.receive(receiveBuffer);
               //客户端每次请求到receiveBuffer里
                //设置buffer指针的下标0。这样就可以从buffer开头，对该buffer进行遍历（读取）了
                receiveBuffer.flip();
                //将字节数据转为字符串 
                String msg= charset.decode(receiveBuffer).toString();
                System.out.println(String.format("new data :%s %s %s ",client.getAddress(),client.getPort(),msg));
                //应答client 发送数据到通道中的客户端
                channel.send(ByteBuffer.wrap(reply(msg).getBytes(charset)),client);
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }
    private String reply(String word){
        return "you said :"+word;
    }
    public static void main(String[] args) throws IOException {
            new UDPChatServer().service();
    }
}

客户端代码:

public class UDPChatClient {
    private Integer port=8000;
    private String host="localhost";
    //UDP socket
    private DatagramSocket socket;
    private InetAddress address;
    private Charset charset=Charset.forName("UTF-8");
    
    public UDPChatClient() throws IOException {
        socket=new DatagramSocket();
        //设置服务器的地址
        address=InetAddress.getByName(host);
        System.out.println("connection ok");
    }
    public static void main(String[] args) throws IOException {
        new UDPChatClient().say();
    }
    private void say() throws IOException {
        BufferedReader localreader=new BufferedReader(new InputStreamReader(System.in));

        String word;
        while ((word=localreader.readLine())!=null){
            // 将string转为byte数组 发送udp包
            byte[] data=word.getBytes(charset);
            //组装包指定ip和端口的数据包
            DatagramPacket outputPacket=new DatagramPacket(data,data.length,address,port);
            //发送
            socket.send(outputPacket);
            //接收udp包放到byte数组中
            DatagramPacket inputPacket=new DatagramPacket(new byte[1024],1024);
            socket.receive(inputPacket);
            //打印获取的数据
            System.out.println(new String(inputPacket.getData(),0,inputPacket.getLength(),charset));
            
            //客户端主动关闭
            if (word.equals("bye")){
                socket.close();
                break;
            }
            
        }
    }
}