Netty source code practice
To learn netty, you can start from the netty-example module of netty source code.
netty-example has an example echo, which is very suitable for introductory learning.
Here it is slightly modified and used as an example for learning.
Introduce dependency packages:
<dependency>
<groupId>io.netty</groupId>
<artifactId>netty-all</artifactId>
<version>4.1.29.Final</version>
</dependency>
Server
After receiving the client’s message, the server will respond.
- EchoServer:
/**
* After receiving the client's message, the server will respond.
*/
public final class EchoServer {
/**
* port
*/
static final int PORT = Integer.parseInt(System.getProperty("port", "8007"));
public static void main(String[] args) throws Exception {
//Configure EventLoopGroup
// Master-slave Reactor multi-thread mode, bossGroup is the master Reactor, workerGroup is the slave Reactor
EventLoopGroup bossGroup = new NioEventLoopGroup(1);
EventLoopGroup workerGroup = new NioEventLoopGroup();
try {
//Initialize the server's boot class ServerBootstrap
ServerBootstrap serverBootstrap = new ServerBootstrap();
//Specify EventLoopGroup
serverBootstrap.group(bossGroup, workerGroup)
//Specify channel
.channel(NioServerSocketChannel.class)
.option(ChannelOption.SO_BACKLOG, 100)
//Specify ChannelHandler for processing channel
.handler(new LoggingHandler(LogLevel.INFO))
.childHandler(new ChannelInitializer<SocketChannel>() {
@Override
public void initChannel(SocketChannel ch) throws Exception {
//ChannelPipeline, based on the responsibility chain model, can add multiple ChannelHandlers
ChannelPipeline channelPipeline = ch.pipeline();
//channelPipeline.addLast(new LoggingHandler(LogLevel.INFO));
//ChannelHandler, used to process channels, process received data, and implement business logic.
channelPipeline.addLast(new EchoServerHandler());
}
});
// Start the server and bind the server to the port on which it will listen for connection requests.
ChannelFuture channelFuture = serverBootstrap.bind(PORT).sync();
// Wait until the server socket is closed
channelFuture.channel().closeFuture().sync();
} finally {
//Close all eventLoops and terminate threads
bossGroup.shutdownGracefully();
workerGroup.shutdownGracefully();
}
}
}
- EchoServerHandler:
ChannelHandler is used to process channels and implement business logic.
/**
* ChannelHandler on the server side.
*
* ChannelHandler, used to process channels, process received data, and implement business logic.
* Inherit ChannelInboundHandlerAdapter to define methods for responding to inbound events.
*
*/
@Sharable
public class EchoServerHandler extends ChannelInboundHandlerAdapter {
/**
* channelRead(): Read the message passed in by channel
*
*/
@Override
public void channelRead(ChannelHandlerContext ctx, Object msg) {
ByteBuf buf= (ByteBuf) msg;
log.info("Message from client: " + buf.toString(CharsetUtil.UTF_8) + "\
");
}
/**
* channelReadComplete(): Indicates that the current ChannelHandler has finished reading.
* After execution, it will automatically jump to the next ChannelHandler in ChannelPipeline.
*
*/
@Override
public void channelReadComplete(ChannelHandlerContext ctx) {
//Return data to the client, writeAndFlush() can also be split into write(msg) and flush()
ctx.writeAndFlush(Unpooled.copiedBuffer("I'm happy to see you too^_^",CharsetUtil.UTF_8));
}
/**
* exceptionCaught(): Called when an exception is thrown during the read operation.
*
*/
@Override
public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) {
//Close the connection when an exception occurs
cause.printStackTrace();
ctx.close();
}
}
Client
In the following example, the client sends a message to the server.
- EchoClient:
/**
* client. Send data to the server and receive the response from the server.
*
*/
public final class EchoClient {
static final String HOST = System.getProperty("host", "127.0.0.1");
static final int PORT = Integer.parseInt(System.getProperty("port", "8007"));
static final int SIZE = Integer.parseInt(System.getProperty("size", "256"));
public static void main(String[] args) throws Exception {
EventLoopGroup group = new NioEventLoopGroup();
try {
Bootstrap bootstrap = new Bootstrap();
bootstrap.group(group)
.channel(NioSocketChannel.class)
.option(ChannelOption.TCP_NODELAY, true)
.handler(new ChannelInitializer<SocketChannel>() {
@Override
public void initChannel(SocketChannel socketChannel) throws Exception {
ChannelPipeline channelPipeline = socketChannel.pipeline();
//channelPipeline.addLast(new LoggingHandler(LogLevel.INFO));
//ChannelHandler, used to process channels, process received data, and implement business logic.
channelPipeline.addLast(new EchoClientHandler());
}
});
//Open the client and connect to the port of the server
ChannelFuture channelFuture = bootstrap.connect(HOST, PORT).sync();
channelFuture.channel().closeFuture().sync();
} finally {
group.shutdownGracefully();
}
}
}
- EchoClientHandler:
/**
* Client's ChannelHandler.
*/
public class EchoClientHandler extends ChannelInboundHandlerAdapter {
/**
* channelActive() will be called after the connection between the client and the server is established.
*
*/
@Override
public void channelActive(ChannelHandlerContext ctx) {
ByteBuf firstMessage = Unpooled.buffer(EchoClient.SIZE);
byte[] bytes = "Nice to meet you^_^\
".getBytes(CharsetUtil.UTF_8);
firstMessage.writeBytes(bytes);
//Send data to server
ctx.writeAndFlush(firstMessage);
}
@Override
public void channelRead(ChannelHandlerContext ctx, Object msg) {
ByteBuf buf = (ByteBuf) msg;
log.info("Message from the server: " + buf.toString(CharsetUtil.UTF_8));
}
@Override
public void channelReadComplete(ChannelHandlerContext ctx) {
ctx.flush();
}
@Override
public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) {
cause.printStackTrace();
ctx.close();
}
}
Execution:
Start the server first, then the client.
The server receives information from the client:
11:25:03.081 [nioEventLoopGroup-3-1] INFO com.example.demo.netty.echo.EchoServerHandler - Message from client: Nice to meet you^_^
The client receives the reply from the server:
11:25:03.091 [nioEventLoopGroup-2-1] INFO com.example.demo.netty.echo.EchoClientHandler - Message from the server: I am also very happy to meet you^_^
Netty common classes
The above example uses Netty’s commonly used classes.
For details, see: https://blog.csdn.net/sinat_32502451/article/details/133934402
Reference materials:
https://zhuanlan.zhihu.com/p/415450910