相信如果是搞java的大伙在工作一两年后一定听过
netty的大名，使用netty我们可以简单快速的开发出tcp、udp连接协议的程序。
本文带给大家一个netty程序的server端实战演练，麻雀虽小，五脏俱全，具体讲解都在代码中
pom配置
<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<groupId>com.wayn.nettyproject</groupId>
<artifactId>netty-project</artifactId>
<version>1.0-SNAPSHOT</version>
<name>netty-project</name>
<!-- FIXME change it to the project's website -->
<url>http://www.example.com</url>
<properties>
<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
<maven.compiler.source>1.8</maven.compiler.source>
<maven.compiler.target>1.8</maven.compiler.target>
</properties>
<dependencies>
<!--netty依赖-->
<dependency>
<groupId>io.netty</groupId>
<artifactId>netty-all</artifactId> <!-- Use 'netty-all' for 4.0 or above -->
<version>4.1.72.Final</version>
</dependency>
<!--lombok 依赖-->
<dependency>
<groupId>org.projectlombok</groupId>
<artifactId>lombok</artifactId>
<version>1.18.22</version>
</dependency>
<!--##### log4j2 start ####-->
<!--log4j2核心包-->
<!-- https://mvnrepository.com/artifact/org.apache.logging.log4j/log4j-core -->
<dependency>
<groupId>org.apache.logging.log4j</groupId>
<artifactId>log4j-core</artifactId>
<version>2.17.1</version>
</dependency>
<!--用于与slf4j保持桥接（里面自动依赖了slf4j-api）-->
<dependency>
<groupId>org.apache.logging.log4j</groupId>
<artifactId>log4j-slf4j-impl</artifactId>
<version>2.17.1</version>
</dependency>
<!-- 异步日志，需要加入disruptor依赖 -->
<dependency>
<groupId>com.lmax</groupId>
<artifactId>disruptor</artifactId>
<version>3.4.4</version>
</dependency>
<!--##### log4j2 end ####-->
<!-- fastjson -->
<dependency>
<groupId>com.alibaba</groupId>
<artifactId>fastjson</artifactId>
<version>1.2.79</version>
</dependency>
<dependency>
<groupId>cn.hutool</groupId>
<artifactId>hutool-all</artifactId>
<version>5.7.18</version>
</dependency>
</dependencies>
<build>
</build>
</project>
tcp服务端
/**
* tcp服务端
*/
@Slf4j
public class NettyServer {
// 绑定端口
private static final int port = 99;
// 维护channel列表，将用户信息和channel做绑定，一个channel代表一个tcp连接
private static final Map<String, Object> channelMap = new HashMap<>();
public static void main(String[] args) throws InterruptedException {
// 创建服务端启动器
ServerBootstrap serverBootstrap = new ServerBootstrap();
// 指定连接接收线程，处理所有用户连接，转给工作线程
NioEventLoopGroup boss = null;
// 指定工作线程，处理用户连接
NioEventLoopGroup worker = null;
try {
boss = new NioEventLoopGroup();
worker = new NioEventLoopGroup();
serverBootstrap.group(boss, worker); // 绑定线程组
serverBootstrap.channel(NioServerSocketChannel.class); // 底层使用nio处理
serverBootstrap.childHandler(new ChannelInitializer<NioSocketChannel>() {
protected void initChannel(NioSocketChannel ch) {
// 创建一个心跳检测的handle，服务端创建连接后，5秒内没有收到客户端的心跳就会触发IdleState.READER_IDLE
IdleStateHandler idleStateHandler = new IdleStateHandler(5, 0, 0) {
// 5秒内没有收到客户端的心跳会触发userEventTriggered方法
@Override
public void userEventTriggered(ChannelHandlerContext ctx, Object evt) {
if (evt instanceof IdleStateEvent) {
IdleStateEvent e = (IdleStateEvent) evt;
// 检测是读状态就发送pong消息
if (e.state() == IdleState.READER_IDLE) {
ByteBuf buffer = Unpooled.buffer();
buffer.writeBytes("pong".getBytes(StandardCharsets.UTF_8));
ctx.channel().writeAndFlush(buffer).addListener(ChannelFutureListener.CLOSE_ON_FAILURE);
String id = ctx.channel().id().asLongText();
// 删除channelMap中客户端连接
channelMap.forEach((s, o) -> {
if (s.equals(id)) {
channelMap.remove(s);
}
});
}
}
}
// 发生异常时，关闭连接
@Override
public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) {
log.error(cause.getMessage(), cause);
String id = ctx.channel().id().asLongText();
channelMap.remove(id);
ctx.close();
}
};
// 通过对象实例，而不是new创建，避免大量客户端连接导致浪费空间
ch.pipeline().addLast("idleStateHandler", idleStateHandler);
// 换行符解码器，指定包与包之间的分隔符是"\n"和"\r\n",避免拆包粘包
ch.pipeline().addLast(new LineBasedFrameDecoder(1024));
// netty日志记录，打印包信息
ch.pipeline().addLast(new LoggingHandler(LogLevel.INFO));
// 入站字符解码器
ch.pipeline().addLast("decoder", new StringDecoder(CharsetUtil.UTF_8));
// 自定义解码器，实现自定义业务逻辑，使用SimpleChannelInboundHandler可以避免ByteBuf的回收问题
ch.pipeline().addLast("MyHandle", new SimpleChannelInboundHandler<String>() {
// 连接第一次创建会调用这个方法
@Override
public void channelActive(ChannelHandlerContext ctx) throws Exception {
String id = ctx.channel().id().asLongText();
log.info("客户端建立连接：{}", id);
channelMap.put(id, ctx.channel());
ctx.channel().writeAndFlush("this is come from server!");
super.channelActive(ctx);
}
// 获取来自客户端的数据
@Override
protected void channelRead0(ChannelHandlerContext ctx, String s) {
log.info("收到客户端消息：{}", s);
ctx.channel().writeAndFlush("server reply\r\n");
}
});
// 出站字符编码器
ch.pipeline().addLast("encoder", new StringEncoder(CharsetUtil.UTF_8));
}
});
ChannelFuture channelFuture = serverBootstrap.bind(port).sync().addListener(future -> {
if (future.isSuccess()) {
log.info("server start up on {}", port);
}
});
channelFuture.channel().closeFuture().sync();
} finally {
// 不要忘了在finally中关闭线程组
if (boss != null) {
boss.shutdownGracefully();
}
if (worker != null) {
worker.shutdownGracefully();
}
}
}
}
本地测试
