netty实现Tcp Socket编程。
demo实现功能
客户端向服务端发送消息，服务器接收到消息后向客户端响应。
加入依赖：
<dependency>
<groupId>io.netty</groupId>
<artifactId>netty-all</artifactId>
<version>4.1.10.Final</version>
</dependency>
我是使用gradle构建项目的，所以build.gradle如下：
compile (
'io.netty:netty-all:4.1.10.Final'
)
服务器代码
import io.netty.bootstrap.ServerBootstrap;
import io.netty.channel.ChannelFuture;
import io.netty.channel.EventLoopGroup;
import io.netty.channel.nio.NioEventLoopGroup;
import io.netty.channel.socket.nio.NioServerSocketChannel;
import io.netty.handler.logging.LoggingHandler;
public class MyServer {
public static void main(String[] args) throws Exception {
EventLoopGroup bossGroup = new NioEventLoopGroup();
EventLoopGroup wokerGroup = new NioEventLoopGroup();
try{
ServerBootstrap serverBootstrap = new ServerBootstrap();
//在服务器端的handler()方法表示对bossGroup起作用，而childHandler表示对wokerGroup起作用
serverBootstrap.group(bossGroup,wokerGroup).channel(NioServerSocketChannel.class)
.childHandler(new MyServerInitializer());
ChannelFuture channelFuture = serverBootstrap.bind(8899).sync();
channelFuture.channel().closeFuture().sync();
}finally {
bossGroup.shutdownGracefully();
wokerGroup.shutdownGracefully();
}
}
}
服务器端初始化Initializer
import io.netty.channel.ChannelInitializer;
import io.netty.channel.ChannelPipeline;
import io.netty.channel.socket.SocketChannel;
import io.netty.handler.codec.LengthFieldBasedFrameDecoder;
import io.netty.handler.codec.LengthFieldPrepender;
import io.netty.handler.codec.string.StringDecoder;
import io.netty.handler.codec.string.StringEncoder;
import io.netty.util.CharsetUtil;
public class MyServerInitializer extends ChannelInitializer<SocketChannel>{
@Override
protected void initChannel(SocketChannel ch) throws Exception {
ChannelPipeline pipeline = ch.pipeline();
pipeline.addLast(new LengthFieldBasedFrameDecoder(Integer.MAX_VALUE,0,4,0,4));
pipeline.addLast(new LengthFieldPrepender(4));
//字符串解码
pipeline.addLast(new StringDecoder(CharsetUtil.UTF_8));
//字符串编码
pipeline.addLast(new StringEncoder(CharsetUtil.UTF_8));
//自己定义的处理器
pipeline.addLast(new MyServerHandler());
}
}
服务器端自定义Handler：
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.SimpleChannelInboundHandler;
import java.util.UUID;
public class MyServerHandler extends SimpleChannelInboundHandler<String>{
@Override
protected void channelRead0(ChannelHandlerContext ctx, String msg) throws Exception {
//打印出客户端地址
System.out.println(ctx.channel().remoteAddress()+", "+msg);
ctx.channel().writeAndFlush("form server: "+ UUID.randomUUID());
}
@Override
public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {
cause.printStackTrace();
ctx.close();
}
}
客户端：
import io.netty.bootstrap.Bootstrap;
import io.netty.channel.ChannelFuture;
import io.netty.channel.EventLoopGroup;
import io.netty.channel.nio.NioEventLoopGroup;
import io.netty.channel.socket.nio.NioSocketChannel;
public class MyClient {
public static void main(String[] args) throws Exception{
EventLoopGroup eventLoopGroup = new NioEventLoopGroup();
try{
Bootstrap bootstrap = new Bootstrap();
bootstrap.group(eventLoopGroup).channel(NioSocketChannel.class)
.handler(new MyClientInitializer());
ChannelFuture channelFuture = bootstrap.connect("localhost",8899).sync();
channelFuture.channel().closeFuture().sync();
}finally {
eventLoopGroup.shutdownGracefully();
}
}
}
客户端初始化Initializer
import io.netty.channel.ChannelInitializer;
import io.netty.channel.ChannelPipeline;
import io.netty.channel.socket.SocketChannel;
import io.netty.handler.codec.LengthFieldBasedFrameDecoder;
import io.netty.handler.codec.LengthFieldPrepender;
import io.netty.handler.codec.string.StringDecoder;
import io.netty.handler.codec.string.StringEncoder;
import io.netty.util.CharsetUtil;
public class MyClientInitializer extends ChannelInitializer<SocketChannel> {
@Override
protected void initChannel(SocketChannel ch) throws Exception {
ChannelPipeline pipeline = ch.pipeline();
pipeline.addLast(new LengthFieldBasedFrameDecoder(Integer.MAX_VALUE,0,4,0,4));
pipeline.addLast(new LengthFieldPrepender(4));
pipeline.addLast(new StringDecoder(CharsetUtil.UTF_8));
pipeline.addLast(new StringEncoder(CharsetUtil.UTF_8));
pipeline.addLast(new MyClientHandler());
}
}
客户端自定义Handler：
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.SimpleChannelInboundHandler;
import java.time.LocalDateTime;
public class MyClientHandler extends SimpleChannelInboundHandler<String>{
@Override
protected void channelRead0(ChannelHandlerContext ctx, String msg) throws Exception {
//服务端的远程地址
System.out.println(ctx.channel().remoteAddress());
System.out.println("client output: "+msg);
ctx.writeAndFlush("from client: "+ LocalDateTime.now());
}
/**
* 当服务器端与客户端进行建立连接的时候会触发，如果没有触发读写操作，则客户端和客户端之间不会进行数据通信，也就是channelRead0不会执行，
* 当通道连接的时候，触发channelActive方法向服务端发送数据触发服务器端的handler的channelRead0回调，然后
* 服务端向客户端发送数据触发客户端的channelRead0，依次触发。
*/
@Override
public void channelActive(ChannelHandlerContext ctx) throws Exception {
ctx.writeAndFlush("来自与客户端的问题!");
}
@Override
public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {
cause.printStackTrace();
ctx.close();
}
}
启动客户端和服务端，服务端控制台：
/127.0.0.1:49645, 来自与客户端的问题!
/127.0.0.1:49645, from client: 2017-10-09T23:44:42.493
/127.0.0.1:49645, from client: 2017-10-09T23:44:42.495
/127.0.0.1:49645, from client: 2017-10-09T23:44:42.496
...
客户端控制台：
localhost/127.0.0.1:8899
client output: form server: ca79614c-351c-4aed-9906-532fb19f8286
localhost/127.0.0.1:8899
client output: form server: c66482ff-503b-41e8-a2b1-0de88e856433
localhost/127.0.0.1:8899
...
流程分析：
当客户端和服务端通道建立连接的时候（触发channelActive方法），客户端向服务发送来“自与客户端的问题!”数据，服务器端channelRead0被触发，进行回写数据到客户端触发客户端的channelRead0回调方法被调用，依次往复。
