Netty官方示例之 —— Echo

作者: 辛德瑞拉Dangerous | 来源:发表于2018-12-11 15:12 被阅读0次

Netty官方示例之 —— Echo

本示例没有考虑到读半包的处理，对于功能演示或者测试，没有问题；但是稍加改造进行性能测试或者压力测试，它就不能正确工作了。

[Echo Server端]

$\color{green}{\small\mathbf{EchoServer.java}}$

[EchoServer完整代码]

package io.netty.example.echo;

import io.netty.bootstrap.ServerBootstrap;
import io.netty.channel.ChannelFuture;
import io.netty.channel.ChannelInitializer;
import io.netty.channel.ChannelOption;
import io.netty.channel.ChannelPipeline;
import io.netty.channel.EventLoopGroup;
import io.netty.channel.nio.NioEventLoopGroup;
import io.netty.channel.socket.SocketChannel;
import io.netty.channel.socket.nio.NioServerSocketChannel;
import io.netty.handler.logging.LogLevel;
import io.netty.handler.logging.LoggingHandler;
import io.netty.handler.ssl.SslContext;
import io.netty.handler.ssl.SslContextBuilder;
import io.netty.handler.ssl.util.SelfSignedCertificate;

/**
 * Echoes back any received data from a client.
 */
public final class EchoServer {

    static final boolean SSL = System.getProperty("ssl") != null;
    static final int PORT = Integer.parseInt(System.getProperty("port", "8007"));

    public static void main(String[] args) throws Exception {
        // Configure SSL.
        final SslContext sslCtx;
        if (SSL) {
            SelfSignedCertificate ssc = new SelfSignedCertificate();
            sslCtx = SslContextBuilder.forServer(ssc.certificate(), ssc.privateKey()).build();
        } else {
            sslCtx = null;
        }

        // Configure the server.
        EventLoopGroup bossGroup = new NioEventLoopGroup(1);
        EventLoopGroup workerGroup = new NioEventLoopGroup();
        final EchoServerHandler serverHandler = new EchoServerHandler();
        try {
            ServerBootstrap b = new ServerBootstrap();
            b.group(bossGroup, workerGroup)
             .channel(NioServerSocketChannel.class)
             .option(ChannelOption.SO_BACKLOG, 100)
             .handler(new LoggingHandler(LogLevel.INFO))
             .childHandler(new ChannelInitializer<SocketChannel>() {
                 @Override
                 public void initChannel(SocketChannel ch) throws Exception {
                     ChannelPipeline p = ch.pipeline();
                     if (sslCtx != null) {
                         p.addLast(sslCtx.newHandler(ch.alloc()));
                     }
                     //p.addLast(new LoggingHandler(LogLevel.INFO));
                     p.addLast(serverHandler);
                 }
             });

            // Start the server.
            ChannelFuture f = b.bind(PORT).sync();

            // Wait until the server socket is closed.
            f.channel().closeFuture().sync();
        } finally {
            // Shut down all event loops to terminate all threads.
            bossGroup.shutdownGracefully();
            workerGroup.shutdownGracefully();
        }
    }
}

[EchoServer具体分析]

EventLoopGroup bossGroup = new NioEventLoopGroup(1);
EventLoopGroup workerGroup = new NioEventLoopGroup();

创建了2个 $\color{green}{\small\mathbf{NioEventLoopGroup}}$ 实例，NioEventLoopGroup是个线程组，它包含了一组NIO线程，专门用来处理网络事件，实际上它们就是Reactor线程组；这里创建2个的原因是：一个用于服务端接受客户端的连接；另一个用于进行SocketChannel的网络读写。

ServerBootstrap b = new ServerBootstrap();

创建 $\color{green}{\small\mathbf{ServerBootstrap}}$ 对象，是Netty用于启动NIO服务端的辅助启动类，目的是降低服务端的开发复杂度。

b.group(bossGroup, workerGroup)
  .channel(NioServerSocketChannel.class)
  .option(ChannelOption.SO_BACKLOG, 100)
  .handler(new LoggingHandler(LogLevel.INFO))
  .childHandler(new ChannelInitializer<SocketChannel>() {
    @Override
    public void initChannel(SocketChannel ch) throws Exception {
      ChannelPipeline p = ch.pipeline();
          if (sslCtx != null) {
             p.addLast(sslCtx.newHandler(ch.alloc()));
          }
          //p.addLast(new LoggingHandler(LogLevel.INFO));
          p.addLast(serverHandler);
     }
 });

dsfsdfsdfd

// Start the server.
ChannelFuture f = b.bind(PORT).sync();

服务端启动辅助类配置完成之后，调用它的bind方法绑定监听端口，随后调用它的同步阻塞方法sync等待绑定操作完成。完成之后Netty会返回一个ChannelFuture，它的功能类似于JDK的java.util.concurrent.Future，主要用于异步操作通知回调。

// Wait until the server socket is closed.
f.channel().closeFuture().sync();

用此方法进行阻塞，等待服务端链路关闭之后，main函数退出。

// Shut down all event loops to terminate all threads.
bossGroup.shutdownGracefully();
workerGroup.shutdownGracefully();

调用NIO线程组的 shutdownGracefully进行优雅的退出，并释放相关联的资源。

$\color{green}{\small\mathbf{EchoServerHandler.java}}$

[EchoServerHandler完整代码]

package io.netty.example.echo;

import io.netty.buffer.ByteBuf;
import io.netty.buffer.Unpooled;
import io.netty.channel.ChannelHandler.Sharable;
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.ChannelInboundHandlerAdapter;

import java.io.UnsupportedEncodingException;
import java.util.Date;

/**
 * Handler implementation for the echo server.
 */
@Sharable
public class EchoServerHandler extends ChannelInboundHandlerAdapter {

    @Override
    public void channelRead(ChannelHandlerContext ctx, Object msg) throws UnsupportedEncodingException {
        ByteBuf buf = (ByteBuf)msg;
        byte[] req = new byte[buf.readableBytes()];
        buf.readBytes(req);
        String body = new String(req, "UTF-8");
        System.out.println("This echo server receive order : " + body);
        String currentTime = "QUERY TIME ORDER".equalsIgnoreCase(body) ? new Date(System.currentTimeMillis()).toString() : "BAD ORDER";
        ByteBuf resp = Unpooled.copiedBuffer(currentTime.getBytes());
        ctx.write(resp);
    }

    @Override
    public void channelReadComplete(ChannelHandlerContext ctx) {
        ctx.flush();
    }

    @Override
    public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) {
        // Close the connection when an exception is raised.
        cause.printStackTrace();
        ctx.close();
    }
}

[EchoServerHandler具体分析]

    @Override
    public void channelRead(ChannelHandlerContext ctx, Object msg) throws UnsupportedEncodingException {
        ByteBuf buf = (ByteBuf)msg;
        byte[] req = new byte[buf.readableBytes()];
        buf.readBytes(req);
        String body = new String(req, "UTF-8");
        System.out.println("This echo server receive order : " + body);
        String currentTime = "QUERY TIME ORDER".equalsIgnoreCase(body) ? new Date(System.currentTimeMillis()).toString() : "BAD ORDER";
        ByteBuf resp = Unpooled.copiedBuffer(currentTime.getBytes());
        ctx.write(resp);
    }

从性能角度考虑，为了防止频繁唤醒Selector进行消息发送，Netty的write方法并不直接将消息写入到SocketChannel中，只是把待发送的消息放到发送缓冲数组中，再通过调用flush方法，将发送缓冲数组中的消息全部写到SocketChannel中。

    @Override
    public void channelReadComplete(ChannelHandlerContext ctx) {
        ctx.flush();
    }

这里调用了ChannelHandlerContext的flush方法，它的作用是将消息发送队列中的消息写入到SocketChannel中发送给对方。

[Echo Client端]

$\color{green}{\small\mathbf{EchoClient.java}}$

[EchoClient完整代码]

package io.netty.example.echo;

import io.netty.bootstrap.Bootstrap;
import io.netty.channel.ChannelFuture;
import io.netty.channel.ChannelInitializer;
import io.netty.channel.ChannelOption;
import io.netty.channel.ChannelPipeline;
import io.netty.channel.EventLoopGroup;
import io.netty.channel.nio.NioEventLoopGroup;
import io.netty.channel.socket.SocketChannel;
import io.netty.channel.socket.nio.NioSocketChannel;
import io.netty.handler.ssl.SslContext;
import io.netty.handler.ssl.SslContextBuilder;
import io.netty.handler.ssl.util.InsecureTrustManagerFactory;

/**
 * Sends one message when a connection is open and echoes back any received
 * data to the server.  Simply put, the echo client initiates the ping-pong
 * traffic between the echo client and server by sending the first message to
 * the server.
 */
public final class EchoClient {

    static final boolean SSL = System.getProperty("ssl") != null;
    static final String HOST = System.getProperty("host", "127.0.0.1");
    static final int PORT = Integer.parseInt(System.getProperty("port", "8007"));
    static final int SIZE = Integer.parseInt(System.getProperty("size", "256"));

    public static void main(String[] args) throws Exception {
        // Configure SSL.git
        final SslContext sslCtx;
        if (SSL) {
            sslCtx = SslContextBuilder.forClient()
                .trustManager(InsecureTrustManagerFactory.INSTANCE).build();
        } else {
            sslCtx = null;
        }

        // Configure the client.
        EventLoopGroup group = new NioEventLoopGroup();
        try {
            Bootstrap b = new Bootstrap();
            b.group(group)
             .channel(NioSocketChannel.class)
             .option(ChannelOption.TCP_NODELAY, true)
             .handler(new ChannelInitializer<SocketChannel>() {
                 @Override
                 public void initChannel(SocketChannel ch) throws Exception {
                     ChannelPipeline p = ch.pipeline();
                     if (sslCtx != null) {
                         p.addLast(sslCtx.newHandler(ch.alloc(), HOST, PORT));
                     }
                     //p.addLast(new LoggingHandler(LogLevel.INFO));
                     p.addLast(new EchoClientHandler());
                 }
             });

            // Start the client.
            ChannelFuture f = b.connect(HOST, PORT).sync();

            // Wait until the connection is closed.
            f.channel().closeFuture().sync();
        } finally {
            // Shut down the event loop to terminate all threads.
            group.shutdownGracefully();
        }
    }
}

[EchoClient具体分析]

ndkjfks

$\color{green}{\small\mathbf{EchoClientHandler.java}}$

[EchoClientHandler完整代码]

package io.netty.example.echo;

import io.netty.buffer.ByteBuf;
import io.netty.buffer.Unpooled;
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.ChannelInboundHandlerAdapter;

import java.io.UnsupportedEncodingException;

/**
 * Handler implementation for the echo client.  It initiates the ping-pong
 * traffic between the echo client and server by sending the first message to
 * the server.
 */
public class EchoClientHandler extends ChannelInboundHandlerAdapter {

    private final ByteBuf firstMessage;

    /**
     * Creates a client-side handler.
     */
    public EchoClientHandler() {
//        firstMessage = Unpooled.buffer(EchoClient.SIZE);
//        for (int i = 0; i < firstMessage.capacity(); i ++) {
//            firstMessage.writeByte((byte) i);
//        }
        byte[] req = "QUERY TIME ORDER".getBytes();
        firstMessage = Unpooled.buffer(req.length);
        firstMessage.writeBytes(req);
    }

    @Override
    public void channelActive(ChannelHandlerContext ctx) {
        ctx.writeAndFlush(firstMessage);
    }

    @Override
    public void channelRead(ChannelHandlerContext ctx, Object msg) throws UnsupportedEncodingException {
        ByteBuf buf = (ByteBuf)msg;
        byte[] req = new byte[buf.readableBytes()];
        buf.readBytes(req);
        String body = new String(req, "UTF-8");
        System.out.println("Now is : " + body);
        ctx.write(msg);
    }

    @Override
    public void channelReadComplete(ChannelHandlerContext ctx) {
       ctx.flush();
    }

    @Override
    public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) {
        // Close the connection when an exception is raised.
        cause.printStackTrace();
        ctx.close();
    }
}

[EchoClientHandler具体分析]

ndkjfks

Netty官方示例之 —— Echo

[Echo Server端]

[EchoServer完整代码]

[EchoServer具体分析]

[EchoServerHandler完整代码]

[EchoServerHandler具体分析]

[Echo Client端]

[EchoClient完整代码]

[EchoClient具体分析]

[EchoClientHandler完整代码]

[EchoClientHandler具体分析]

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