Netty入门之客户端与服务端通信(二)

Netty入门之客户端与服务端通信(二)

一.简介

　　在上一篇博文中笔者写了关于Netty入门级的Hello World程序。书接上回，本博文是关于客户端与服务端的通信，感觉也没什么好说的了，直接上代码吧。

二.客户端与服务端的通信

2.1 服务端启动程序

public class MyServer {
public static void main(String[] args) throws InterruptedException {
EventLoopGroup bossGroup = new NioEventLoopGroup();
EventLoopGroup workerGroup = new NioEventLoopGroup();

try{
ServerBootstrap serverBootstrap = new ServerBootstrap();

serverBootstrap.group(bossGroup, workerGroup)
.channel(NioServerSocketChannel.class)
.childHandler(new MyInitializer());

ChannelFuture channelFuture = serverBootstrap.bind(8899).sync();
channelFuture.channel().closeFuture().sync();
}finally{
bossGroup.shutdownGracefully();
workerGroup.shutdownGracefully();
}
}
}

2.2 服务端通道初始化程序

public class MyInitializer extends ChannelInitializer<SocketChannel>{

@Override
protected void initChannel(SocketChannel ch) throws Exception {
ChannelPipeline pipeline =  ch.pipeline();
/**
* LengthFieldBasedFrameDecoder: 基于长度属性的帧解码器。
* 客户端传递过来的数据格式为：
*  BEFORE DECODE (14 bytes)         AFTER DECODE (14 bytes)
*    +--------+----------------+      +--------+----------------+
*    | Length | Actual Content |----->| Length | Actual Content |
*    | 0x000C | "HELLO, WORLD" |      | 0x000C | "HELLO, WORLD" |
*    +--------+----------------+      +--------+----------------+
* 5个参数依次为：1.(maxFrameLength)每帧数据的最大长度.
*              2.(lengthFieldOffset)length属性在帧中的偏移量。
*           3.(lengthFieldLength)length属性的长度，需要与客户端 LengthFieldPrepender设置的长度一致，
*               值的取值只能为1, 2, 3, 4, 8
*           4.(lengthAdjustment)长度调节值, 当信息长度包含长度时候，用于修正信息的长度。
*           5.(initialBytesToStrip)在获取真实的内容的时候，需要忽略的长度(通常就是length的长度)。
*
* 参考： http://blog.csdn.net/educast/article/details/47706599 */
pipeline.addLast("lengthFieldBasedFrameDecoder",
new LengthFieldBasedFrameDecoder(Integer.MAX_VALUE, 0, 2, 0, 2));
/**
* LengthFieldPrepender: length属性在帧中的长度。只能为1,2,3,4,8。
* 该值与对应的客户端(或者服务端)在解码时候使用LengthFieldBasedFrameDecoder中所指定的lengthFieldLength
* 的值要保持一致。
*/
pipeline.addLast("lengthFieldPrepender", new LengthFieldPrepender(3));
//StringDecoder字符串的解码器, 主要用于处理编码格式
pipeline.addLast("stringDecoder", new StringDecoder(CharsetUtil.UTF_8));
//StringDecoder字符串的编码器，主要用于指定字符串的编码格式
pipeline.addLast("stringEncoder", new StringEncoder(CharsetUtil.UTF_8));

pipeline.addLast(new MyHandler()); //自定义的Handler
}
}

2.3 自定义Handler

public class MyHandler extends SimpleChannelInboundHandler<String>{

@Override
protected void channelRead0(ChannelHandlerContext ctx, String msg) throws Exception {
System.out.println(ctx.channel().remoteAddress() + ":" + msg);
ctx.channel().writeAndFlush("from server: 草泥马");
}

@Override
public void handlerAdded(ChannelHandlerContext ctx) throws Exception {
System.out.println(System.currentTimeMillis() + "********");
System.out.println("server handler added**********");
}

@Override
public void channelRegistered(ChannelHandlerContext ctx) throws Exception {
System.out.println(System.currentTimeMillis() + "********");
System.out.println("server channel register****");
}

@Override
public void channelActive(ChannelHandlerContext ctx) throws Exception {
System.out.println(System.currentTimeMillis() + "********");
System.out.println("server channel actieve****");
}

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

2.4客户端启动程序

public class MyClient {
public static void main(String[] args) throws InterruptedException {
EventLoopGroup eventLoopGroup = new NioEventLoopGroup();

try{
Bootstrap bootstrap = new Bootstrap();
bootstrap.group(eventLoopGroup).channel(NioSocketChannel.class).handler(new ClientInitializer());

ChannelFuture channelFuture = bootstrap.connect("127.0.0.1", 8899).sync();
channelFuture.channel().closeFuture().sync();
}finally{
eventLoopGroup.shutdownGracefully();
}
}
}

2.5客户端通道初始化

public class ClientInitializer extends ChannelInitializer<SocketChannel>{

@Override
protected void initChannel(SocketChannel ch) throws Exception {
ChannelPipeline pipeline =  ch.pipeline();
pipeline.addLast("lengthFieldBasedFrameDecoder",
new LengthFieldBasedFrameDecoder(Integer.MAX_VALUE, 0, 2, 0, 2));
pipeline.addLast("lengthFieldPrepender", new LengthFieldPrepender(3));
pipeline.addLast("stringDecoder", new StringDecoder(CharsetUtil.UTF_8));
pipeline.addLast("stringEncoder", new StringEncoder(CharsetUtil.UTF_8));

pipeline.addLast(new MyClientHandler());
}
}

2.5客户端自定义Handler

public class MyClientHandler extends SimpleChannelInboundHandler<String>{

@Override
protected void channelRead0(ChannelHandlerContext ctx, String msg) throws Exception {
System.out.println(ctx.channel().remoteAddress());
System.out.println(msg);
ctx.channel().writeAndFlush("to Server: 草泥马");
}

@Override
public void channelActive(ChannelHandlerContext ctx) throws Exception {
System.out.println(System.currentTimeMillis() + "...........");
ctx.channel().writeAndFlush("来自于客户端的问候！");
System.out.println("client channel Active...");
}

@Override
public void handlerAdded(ChannelHandlerContext ctx) throws Exception {
System.out.println(System.currentTimeMillis() + "...........");
System.out.println("client hanlder added...");
}

@Override
public void channelRegistered(ChannelHandlerContext ctx) throws Exception {
System.out.println(System.currentTimeMillis() + "...........");
System.out.println("client channel register...");
}

@Override
public void channelInactive(ChannelHandlerContext ctx) throws Exception {
System.out.println("client channel inactive...");
}

@Override
public void channelUnregistered(ChannelHandlerContext ctx) throws Exception {
System.out.println("client channel unregister...");
}

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

三. 运行测试

运行服务端启动代码，然后在运行客户端启动代码，就可以看见千万只"草泥马"在崩腾。