netty写Echo Server & Client完整步骤教程（图文）
2024-09-08 03:07:49
1.创建Maven工程
1.1 父节点的pom.xml代码（root pom文件)
1 <?xml version="1.0" encoding="UTF-8"?>
2 <project xmlns="http://maven.apache.org/POM/4.0.0"
3 xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
4 xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
5 <modelVersion>4.0.0</modelVersion>
6
7 <groupId>org.example</groupId>
8 <artifactId>echo_netty</artifactId>
9 <packaging>pom</packaging>
10 <version>1.0-SNAPSHOT</version>
11 <modules>
12 <module>netty-server</module>
13 <module>netty-client</module>
14 </modules>
15
16 </project>
1.2 子工程netty-server的pom.xml文件代码
1 <?xml version="1.0" encoding="UTF-8"?>
2 <project xmlns="http://maven.apache.org/POM/4.0.0"
3 xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
4 xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
5 <parent>
6 <artifactId>echo_netty</artifactId>
7 <groupId>org.example</groupId>
8 <version>1.0-SNAPSHOT</version>
9 </parent>
10 <modelVersion>4.0.0</modelVersion>
11
12 <artifactId>netty-server</artifactId>
13
14
15 </project>
1.3 子工程netty-client的pom.xml文件代码
1 <?xml version="1.0" encoding="UTF-8"?>
2 <project xmlns="http://maven.apache.org/POM/4.0.0"
3 xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
4 xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
5 <parent>
6 <artifactId>echo_netty</artifactId>
7 <groupId>org.example</groupId>
8 <version>1.0-SNAPSHOT</version>
9 </parent>
10 <modelVersion>4.0.0</modelVersion>
11
12 <artifactId>netty-client</artifactId>
13
14
15 </project>
1.4 修改父工程的pom.xml，修改后如下所示：
1 <?xml version="1.0" encoding="UTF-8"?>
2 <project xmlns="http://maven.apache.org/POM/4.0.0"
3 xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
4 xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
5 <modelVersion>4.0.0</modelVersion>
6
7 <groupId>org.example</groupId>
8 <artifactId>echo_netty</artifactId>
9 <packaging>pom</packaging>
10 <version>1.0-SNAPSHOT</version>
11 <modules>
12 <module>netty-server</module>
13 <module>netty-client</module>
14 </modules>
15
16 <properties>
17 <echo-server.hostname>localhost</echo-server.hostname>
18 <echo-server.port>9999</echo-server.port>
19 </properties>
20
21 <dependencies>
22 <dependency>
23 <groupId>io.netty</groupId>
24 <artifactId>netty-all</artifactId>
25 <version>4.1.10.Final</version>
26 <scope>compile</scope>
27 </dependency>
28 </dependencies>
29
30 <build>
31 <plugins>
32 <plugin>
33 <artifactId>maven-compiler-plugin</artifactId>
34 </plugin>
35 <plugin>
36 <artifactId>maven-failsafe-plugin</artifactId>
37 </plugin>
38 <plugin>
39 <artifactId>maven-surefire-plugin</artifactId>
40 </plugin>
41 <plugin>
42 <groupId>org.codehaus.mojo</groupId>
43 <artifactId>exec-maven-plugin</artifactId>
44 </plugin>
45 </plugins>
46 </build>
47 </project>
1.5 修改netty-server的pom.xml，修改后如下所示：
1 <?xml version="1.0" encoding="UTF-8"?>
2 <project xmlns="http://maven.apache.org/POM/4.0.0"
3 xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
4 xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
5 <parent>
6 <artifactId>echo_netty</artifactId>
7 <groupId>org.example</groupId>
8 <version>1.0-SNAPSHOT</version>
9 </parent>
10 <modelVersion>4.0.0</modelVersion>
11
12 <artifactId>netty-server</artifactId>
13
14 <build>
15 <plugins>
16 <plugin>
17 <groupId>org.codehaus.mojo</groupId>
18 <artifactId>exec-maven-plugin</artifactId>
19 <executions>
20 <execution>
21 <id>run-server</id>
22 <goals>
23 <goal>java</goal>
24 </goals>
25 </execution>
26 </executions>
27 <configuration>
28 <mainClass>com.echo.server.EchoServer</mainClass>
29 <arguments>
30 <argument>${echo-server.port}</argument>
31 </arguments>
32 </configuration>
33 </plugin>
34 </plugins>
35 </build>
36
37 </project>
1.6 修改netty-client的pom.xml，修改后如下所示：
1 <?xml version="1.0" encoding="UTF-8"?>
2 <project xmlns="http://maven.apache.org/POM/4.0.0"
3 xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
4 xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
5 <parent>
6 <artifactId>echo_netty</artifactId>
7 <groupId>org.example</groupId>
8 <version>1.0-SNAPSHOT</version>
9 </parent>
10 <modelVersion>4.0.0</modelVersion>
11
12 <artifactId>netty-client</artifactId>
13
14 <build>
15 <plugins>
16 <plugin>
17 <groupId>org.codehaus.mojo</groupId>
18 <artifactId>exec-maven-plugin</artifactId>
19 <executions>
20 <execution>
21 <id>run-server</id>
22 <goals>
23 <goal>java</goal>
24 </goals>
25 </execution>
26 </executions>
27 <configuration>
28 <mainClass>com.echo.client.EchoClient</mainClass>
29 <arguments>
30 <argument>${echo-server.hostname}</argument>
31 <argument>${echo-server.port}</argument>
32 </arguments>
33 </configuration>
34 </plugin>
35 </plugins>
36 </build>
37
38 </project>
2. 开始写netty客户端的代码
到这里的时候，项目的结构应该是这个样子的，然后让我们修改一下EchoClient.java和EchoClientHandler.java文件的内容，修改后最终代码放在下面，大家请看：
2.1 EchoClient.java的最终代码
1 package com.echo.client;
2
3 import java.net.InetSocketAddress;
4
5 import com.echo.client.handler.EchoClientHandler;
6 import io.netty.bootstrap.Bootstrap;
7 import io.netty.channel.ChannelFuture;
8 import io.netty.channel.ChannelInitializer;
9 import io.netty.channel.EventLoopGroup;
10 import io.netty.channel.nio.NioEventLoopGroup;
11 import io.netty.channel.socket.SocketChannel;
12 import io.netty.channel.socket.nio.NioSocketChannel;
13
14 public class EchoClient {
15
16 private final String host;
17 private final int port;
18
19 public EchoClient(String host, int port) {
20 this.host = host;
21 this.port = port;
22 }
23
24 public static void main(String[] args) throws Exception {
25 if (args.length != 2) {
26 System.err.println(
27 "Usage: " + EchoClient.class.getSimpleName() +
28 " <host> <port>");
29 return;
30 }
31 String host = args[0];
32 int port = Integer.parseInt(args[1]);
33 new EchoClient(host, port).start();
34 }
35
36 public void start() throws Exception {
37 EventLoopGroup group = new NioEventLoopGroup();
38 try {
39 Bootstrap b = new Bootstrap();
40 b.group(group)
41 .channel(NioSocketChannel.class)
42 .remoteAddress(new InetSocketAddress(host, port))
43 .handler(new ChannelInitializer<SocketChannel>() {
44
45 @Override
46 protected void initChannel(SocketChannel ch) throws Exception {
47 ch.pipeline().addLast(new EchoClientHandler());
48 }
49
50 });
51 ChannelFuture f = b.connect().sync();
52 f.channel().closeFuture().sync();
53 } finally {
54 group.shutdownGracefully().sync();
55 }
56 }
57
58 }
2.2 EchoClientHandler.java的最终代码
1 package com.echo.client.handler;
2
3 import io.netty.buffer.ByteBuf;
4 import io.netty.buffer.Unpooled;
5 import io.netty.channel.ChannelHandler.Sharable;
6 import io.netty.channel.ChannelHandlerContext;
7 import io.netty.channel.SimpleChannelInboundHandler;
8 import io.netty.util.CharsetUtil;
9
10 @Sharable
11 public class EchoClientHandler extends SimpleChannelInboundHandler<ByteBuf> {
12
13 @Override
14 public void channelActive(ChannelHandlerContext ctx) throws Exception {
15 ctx.writeAndFlush(Unpooled.copiedBuffer("Netty rocks!", CharsetUtil.UTF_8));
16 }
17
18 @Override
19 protected void channelRead0(ChannelHandlerContext ctx, ByteBuf in) throws Exception {
20 System.out.println("Client received: " + in.toString(CharsetUtil.UTF_8));
21 }
22
23 @Override
24 public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {
25 cause.printStackTrace();
26 ctx.close();
27 }
28
29 }
到这的时候，如果有报错的话，一般是maven没有刷新导致的。
解决方法是，打开父工程的pom.xml ,然后点击idea的右侧的maven刷新按钮，如下图所示
至此，EchoClient端的代码就写好了。暂时先不启动，先写好EchoServer，再一起启动。下面介绍EchoServer端的代码。
3. 开始写netty服务端的代码
3.2 修改EchoServer.java文件代码，修改后最终代码如下：
1 package com.echo.server;
2
3 import java.net.InetSocketAddress;
4
5 import com.echo.server.handler.EchoServerHandler;
6 import io.netty.bootstrap.ServerBootstrap;
7 import io.netty.channel.ChannelFuture;
8 import io.netty.channel.ChannelInitializer;
9 import io.netty.channel.EventLoopGroup;
10 import io.netty.channel.nio.NioEventLoopGroup;
11 import io.netty.channel.socket.SocketChannel;
12 import io.netty.channel.socket.nio.NioServerSocketChannel;
13
14 public class EchoServer {
15
16 private final int port;
17
18 public EchoServer(int port) {
19 this.port = port;
20 }
21
22 public void start() throws Exception {
23 final EchoServerHandler serverHandler = new EchoServerHandler();
24 EventLoopGroup group = new NioEventLoopGroup();
25 try {
26 ServerBootstrap b = new ServerBootstrap();
27 b.group(group)
28 .channel(NioServerSocketChannel.class)
29 .localAddress(new InetSocketAddress(port))
30 .childHandler(new ChannelInitializer<SocketChannel>() {
31
32 @Override
33 protected void initChannel(SocketChannel ch) throws Exception {
34 ch.pipeline().addLast(serverHandler);
35 }
36 });
37 // 此处绑定服务器，并等待绑定完成。对sync()方法的调用将导致当前Thread阻塞，直到绑定完成
38 ChannelFuture f = b.bind().sync();
39 // 由于调用了sync()方法，程序将会阻塞等待，直到服务器的Channel关闭
40 f.channel().closeFuture().sync();
41 } finally {
42 group.shutdownGracefully().sync();
43 }
44 }
45
46 public static void main(String[] args) throws Exception {
47 if (args.length != 1) {
48 System.err.println(
49 "Usage: " + EchoServer.class.getSimpleName() + " <port>"
50 );
51 return;
52 }
53 int port = Integer.parseInt(args[0]);
54 new EchoServer(port).start();
55 }
56
57 }
3.3 修改EchoServerHandler.java文件代码，修改后最终代码如下：
1 package com.echo.server.handler;
2
3 import io.netty.buffer.ByteBuf;
4 import io.netty.buffer.Unpooled;
5 import io.netty.channel.ChannelHandler.Sharable;
6 import io.netty.channel.ChannelFutureListener;
7 import io.netty.channel.ChannelHandlerContext;
8 import io.netty.channel.ChannelInboundHandlerAdapter;
9 import io.netty.util.CharsetUtil;
10
11 // @Sharable标示一个ChannelHandler可以被多个Channel安全共享
12 @Sharable
13 public class EchoServerHandler extends ChannelInboundHandlerAdapter {
14
15 @Override
16 public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
17 ByteBuf in = (ByteBuf) msg;
18 System.out.println(
19 "Server received: " + in.toString(CharsetUtil.UTF_8));
20 // 将接收到的消息写给发送者，即客户端，而不冲刷出站消息
21 ctx.write(in);
22 }
23
24 @Override
25 public void channelReadComplete(ChannelHandlerContext ctx) throws Exception {
26 // 将未决消息冲刷到远程节点，并且关闭该Channel
27 ctx.writeAndFlush(Unpooled.EMPTY_BUFFER)
28 .addListener(ChannelFutureListener.CLOSE);
29 }
30
31 @Override
32 public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {
33 cause.printStackTrace();
34 ctx.close();
35 }
36
37 }
至此，所有的代码已经写好，下一步进行运行测试
4.运行代码
4.1 打包代码
当出现BUILD SUCCESS的时候，代表代码已经打包好了。
4.2 运行server端
出现一直在转圈的时候，代表server端启动成功了
4.3 运行client端
双击运行client端，然后稍等片刻，会发现下图已经出现了
Client received: Netty rocks!
这一行字。说明客户端和服务端通信成功。
接着看一下server端打印的输出，如下图：
可以看到，server端已经输出了从客户端收到的消息！！！
至此，所有的演示都结束了，大家自己动手进行实践吧。
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