五、netty tcp服務端

所有文章

https://www.cnblogs.com/lay2017/p/12922074.html

 

正文

要構建netty的tcp服務端，你需要

1.創建EventLoopGroup

2.配置一個ServerBootStrap

3.創建ChannelInitializer

4.啟動服務

代碼如下

EventLoopGroup group = new NioEventLoopGroup();

try{
    ServerBootstrap serverBootstrap = new ServerBootstrap();
    serverBootstrap.group(group);
    serverBootstrap.channel(NioServerSocketChannel.class);
    serverBootstrap.localAddress(new InetSocketAddress("localhost", 9999));

    serverBootstrap.childHandler(new ChannelInitializer<SocketChannel>() {
        protected void initChannel(SocketChannel socketChannel) throws Exception {
            socketChannel.pipeline().addLast(new HelloServerHandler());
        }
    });
    ChannelFuture channelFuture = serverBootstrap.bind().sync();
    channelFuture.channel().closeFuture().sync();
} catch(Exception e){
    e.printStackTrace();
} finally {
    group.shutdownGracefully().sync();
}

創建EventLoopGroup

第一步是創建EventLoopGroup，相對比較簡單，如

EventLoopGroup group = new NioEventLoopGroup();

創建ServerBootstrap

第二步是創建ServerBootstrap

ServerBootstrap serverBootstrap = new ServerBootstrap();
serverBootstrap.group(group);
serverBootstrap.channel(NioServerSocketChannel.class);
serverBootstrap.localAddress(new InetSocketAddress("localhost", 9999));

group方法把EventLoopGroup綁定到了ServerBootstrap上

EventLoopGroup是NioEventLoopGroup實現，所以這里要指明channel是NioServerSocketChannel

最后通過InetSocketAddress指明domain + port

創建ChannelInitializer

第三步是創建ChannelInitializer

serverBootstrap.childHandler(new ChannelInitializer<SocketChannel>() {
    protected void initChannel(SocketChannel socketChannel) throws Exception {
        socketChannel.pipeline().addLast(new HelloServerHandler());
    }
});

ChannelInitializer綁定到了serverBootstrap上

pipeline添加ChannelHandler

啟動

最后一步，啟動服務

ChannelFuture channelFuture = serverBootstrap.bind().sync();

bind方法返回ChannelFuture，可以知道綁定到domain  + port什么時候完成。sync方法會等待服務啟動完成

HelloChannelHandler

最后給出HelloChannelHandler代碼

public class HelloServerHandler extends ChannelInboundHandlerAdapter {

    @Override
    public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
        ByteBuf inBuffer = (ByteBuf) msg;

        String received = inBuffer.toString(CharsetUtil.UTF_8);
        System.out.println("Server received: " + received);

        ctx.write(Unpooled.copiedBuffer("Hello " + received, CharsetUtil.UTF_8));
    }

    @Override
    public void channelReadComplete(ChannelHandlerContext ctx) throws Exception {
        ctx.writeAndFlush(Unpooled.EMPTY_BUFFER)
                .addListener(ChannelFutureListener.CLOSE);
    }

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

channelRead方法是從SocketChannel中read數據的時候觸發，channelReadComplete方法是沒有可讀數據的時候觸發，exceptionCaught方法是從socket中read數據或者write數據的時候異常觸發