TcpDnsServer Class — netty Architecture

Source Code

example/src/main/java/io/netty/example/dns/tcp/TcpDnsServer.java lines 55–168

public final class TcpDnsServer {
    private static final String QUERY_DOMAIN = "www.example.com";
    private static final int DNS_SERVER_PORT = 53;
    private static final String DNS_SERVER_HOST = "127.0.0.1";
    private static final byte[] QUERY_RESULT = new byte[]{(byte) 192, (byte) 168, 1, 1};

    public static void main(String[] args) throws Exception {
        ServerBootstrap bootstrap = new ServerBootstrap().group(
                new MultiThreadIoEventLoopGroup(NioIoHandler.newFactory()))
                .channel(NioServerSocketChannel.class)
                .handler(new LoggingHandler(LogLevel.INFO))
                .childHandler(new ChannelInitializer<Channel>() {
                    @Override
                    protected void initChannel(Channel ch) throws Exception {
                        ch.pipeline().addLast(new TcpDnsQueryDecoder(), new TcpDnsResponseEncoder(),
                                new SimpleChannelInboundHandler<DnsQuery>() {
                                    @Override
                                    protected void channelRead0(ChannelHandlerContext ctx,
                                                                DnsQuery msg) throws Exception {
                                        DnsQuestion question = msg.recordAt(DnsSection.QUESTION);
                                        System.out.println("Query domain: " + question);

                                        //always return 192.168.1.1
                                        ctx.writeAndFlush(newResponse(msg, question, 600, QUERY_RESULT));
                                    }

                                    private DefaultDnsResponse newResponse(DnsQuery query,
                                                                           DnsQuestion question,
                                                                           long ttl, byte[]... addresses) {
                                        DefaultDnsResponse response = new DefaultDnsResponse(query.id());
                                        response.addRecord(DnsSection.QUESTION, question);

                                        for (byte[] address : addresses) {
                                            DefaultDnsRawRecord queryAnswer = new DefaultDnsRawRecord(
                                                    question.name(),
                                                    DnsRecordType.A, ttl, Unpooled.wrappedBuffer(address));
                                            response.addRecord(DnsSection.ANSWER, queryAnswer);
                                        }
                                        return response;
                                    }
                                });
                    }
                });
        final Channel channel = bootstrap.bind(DNS_SERVER_PORT).channel();
        Executors.newSingleThreadScheduledExecutor().schedule(new Runnable() {
            @Override
            public void run() {
                try {
                    clientQuery();
                    channel.close();
                } catch (Exception e) {
                    e.printStackTrace();
                }
            }
        }, 1000, TimeUnit.MILLISECONDS);
        channel.closeFuture().sync();
    }

    // copy from TcpDnsClient.java
    private static void clientQuery() throws Exception {
        EventLoopGroup group = new MultiThreadIoEventLoopGroup(NioIoHandler.newFactory());
        try {
            Bootstrap b = new Bootstrap();
            b.group(group)
                    .channel(NioSocketChannel.class)
                    .handler(new ChannelInitializer<SocketChannel>() {
                        @Override
                        protected void initChannel(SocketChannel ch) {
                            ch.pipeline().addLast(new TcpDnsQueryEncoder())
                                    .addLast(new TcpDnsResponseDecoder())
                                    .addLast(new SimpleChannelInboundHandler<DefaultDnsResponse>() {
                                        @Override
                                        protected void channelRead0(ChannelHandlerContext ctx, DefaultDnsResponse msg) {
                                            try {
                                                handleQueryResp(msg);
                                            } finally {
                                                ctx.close();
                                            }
                                        }
                                    });
                        }