netty realizes group chat

Keywords: Java Netty codec socket

[overview]

Implement a group chat tool. The client messages participating in the chat are broadcast through the server.

It mainly consists of two parts: chat server and chat client.

Chat server function overview:

1. Monitor the access and disconnection of all clients

2. When client A accesses the chat room, send the access message to other clients except client A

3. When client A exits the chat room, send the exit message to other clients except client A

4. When client A sends A message to the chat room, forward the message to other clients except client A

Chat client function overview:

1. Send message to chat server

2. Receive all messages sent by chat server

[pom dependence]

        <!--netty-->
        <dependency>
            <groupId>io.netty</groupId>
            <artifactId>netty-all</artifactId>
            <version>4.1.36.Final</version>
        </dependency>
        <!--lombok rely on-->
        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
            <version>1.18.6</version>
            <scope>provided</scope>
        </dependency>

[server initiator ChatServer]

package com.test.server;

import io.netty.bootstrap.ServerBootstrap;
import io.netty.channel.*;
import io.netty.channel.nio.NioEventLoopGroup;
import io.netty.channel.socket.SocketChannel;
import io.netty.channel.socket.nio.NioServerSocketChannel;
import io.netty.handler.codec.LineBasedFrameDecoder;
import io.netty.handler.codec.string.StringDecoder;
import io.netty.handler.codec.string.StringEncoder;

/**
 * Group chat server
 *
 */
public class ChatServer {
    private final int port;

    public ChatServer(int port) {
        this.port = port;
    }

    public void start() throws InterruptedException {
        EventLoopGroup parentGroup = new NioEventLoopGroup();
        EventLoopGroup childGroup = new NioEventLoopGroup();

        try {
            ServerBootstrap serverBootstrap = new ServerBootstrap();
            serverBootstrap.group(parentGroup, childGroup).channel(NioServerSocketChannel.class).childHandler(new ChannelInitializer<SocketChannel>() {

                protected void initChannel(SocketChannel sc) throws Exception {
                    ChannelPipeline pipeline = sc.pipeline();
                    //Add a row based decoder
                    pipeline.addLast(new LineBasedFrameDecoder(2048));
                    pipeline.addLast(new StringDecoder());
                    pipeline.addLast(new StringEncoder());
                    pipeline.addLast(new ChatServerHandler());
                }

            }).option(ChannelOption.SO_BACKLOG, 128).option(ChannelOption.SO_KEEPALIVE, true);
            ChannelFuture future = serverBootstrap.bind(port).sync();
            System.out.println("Server started");
            future.channel().closeFuture().sync();
        } finally {
            parentGroup.shutdownGracefully();
            childGroup.shutdownGracefully();
        }
    }

    public static void main(String[] args) throws InterruptedException {
        new ChatServer(8888).start();
    }
}

[ChatServerHandler]

package com.test.server;

import io.netty.channel.Channel;
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.ChannelInboundHandlerAdapter;
import io.netty.channel.group.ChannelGroup;
import io.netty.channel.group.DefaultChannelGroup;
import io.netty.util.concurrent.GlobalEventExecutor;

/**
 * Handle various situations of chat server
 *
 */
public class ChatServerHandler extends ChannelInboundHandlerAdapter {
    // Create a ChannelGroup，It is a thread safe collection that holds all the connections to the current server Active State Channel
    // GlobalEventExecutor Is a single instance, single thread EventExecutor，Is to ensure that group All of them Channel Processing
    // Thread is the same thread
    private static ChannelGroup group = new DefaultChannelGroup(GlobalEventExecutor.INSTANCE);

    // As long as there are clients Channel If a message is sent to the current server, the execution of the method will be triggered
    @Override
    public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
        // Get the channel
        Channel channel = ctx.channel();
        // Here we want to broadcast messages to all group Clients in Channel
        // The message sent to oneself is different from the message sent to everyone
        group.forEach(ch -> {
            if (ch != channel) {
                ch.writeAndFlush(channel.remoteAddress() + ": " + msg + "\n");
            } else {
                channel.writeAndFlush("me: " + msg + "\n");
            }
        });
    }

    // As long as there are clients Channel If the connection with the server is successful, this method will be executed
    @Override
    public void channelActive(ChannelHandlerContext ctx) throws Exception {
        // Get the current successful connection with the server channel
        Channel channel = ctx.channel();
        System.out.println(channel.remoteAddress() + "---Go online");
        group.writeAndFlush(channel.remoteAddress() + "---Go online\n");
        // Will present channel Add to group in
        group.add(channel);
    }

    // As long as there are clients Channel Disconnect from the server and execute this method
    @Override
    public void channelInactive(ChannelHandlerContext ctx) throws Exception {
        // Get to the currently disconnected Channel
        Channel channel = ctx.channel();
        System.out.println(channel.remoteAddress() + "------Offline");
        group.writeAndFlush(channel.remoteAddress() + "Offline, current online population:" + group.size() + "\n");

        // group It's all stored in Active State Channel，Once a certain Channel The status of is no longer Active，
        // group It is automatically kicked out of the collection, so the following statement does not need to be written
        // remove()The application scenario of the method is to Active State channel Move out group Use time
        // group.remove(channel);
    }

    /**
     * The execution of this method will be triggered when the data in the Channel is abnormal during processing
     *
     * @param ctx   context
     * @param cause Exception object occurred
     * @throws Exception
     */
    @Override
    public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {
        cause.printStackTrace();
        ctx.close();
    }

}

[Client startup class ChatClient]

package com.test.client;

import io.netty.bootstrap.Bootstrap;
import io.netty.channel.ChannelFuture;
import io.netty.channel.ChannelInitializer;
import io.netty.channel.ChannelPipeline;
import io.netty.channel.nio.NioEventLoopGroup;
import io.netty.channel.socket.SocketChannel;
import io.netty.channel.socket.nio.NioSocketChannel;
import io.netty.handler.codec.LineBasedFrameDecoder;
import io.netty.handler.codec.string.StringDecoder;
import io.netty.handler.codec.string.StringEncoder;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;

/**
 * Group chat client
 *
 */
public class ChatClient {
    private final String host;

    private final int port;

    public ChatClient(String host, int port) {
        this.host = host;
        this.port = port;
    }

    public void start() {
        NioEventLoopGroup group = new NioEventLoopGroup();
        Bootstrap bootstrap = new Bootstrap();
        try {
            bootstrap.group(group).channel(NioSocketChannel.class).handler(new ChannelInitializer<SocketChannel>() {
                @Override
                protected void initChannel(SocketChannel ch) throws Exception {
                    ChannelPipeline pipeline = ch.pipeline();
                    pipeline.addLast(new LineBasedFrameDecoder(2048));
                    pipeline.addLast(new StringDecoder());
                    pipeline.addLast(new StringEncoder());
                    pipeline.addLast(new ChatClientHandler());
                }
            });
            ChannelFuture future = bootstrap.connect(host, port).sync();
            // Get keyboard input
            InputStreamReader is = new InputStreamReader(System.in, "UTF-8");
            BufferedReader br = new BufferedReader(is);
            // Write the input to Channel
            while (true) {
                //br.readLine()Execute in fill()Method to get the input data. If the data is not obtained, it will block until the data is obtained
                future.channel().writeAndFlush(br.readLine() + "\r\n");
            }
        } catch (InterruptedException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            group.shutdownGracefully();
        }
    }

    public static void main(String[] args) {
        new ChatClient("127.0.0.1", 8888).start();
    }
}

[ChatClientHandler]

package com.test.client;

import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.SimpleChannelInboundHandler;

/**
 * Client processing
 *
 */
public class ChatClientHandler extends SimpleChannelInboundHandler<String> {
    @Override
    protected void channelRead0(ChannelHandlerContext channelHandlerContext, String s) throws Exception {
        System.out.println(s);
    }

    @Override
    public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {
        ctx.close();
    }
}