Netty斷線重連

最近使用Netty開發一箇中轉服務，需要一直保持與Server端的連線，網路中斷後需要可以自動重連，查詢官網資料，實現方案很簡單，核心思想是在channelUnregistered鉤子函式裡執行重連。

建立連線

需要把configureBootstrap重構為一個函式，方便後續複用

 EventLoopGroup group = new NioEventLoopGroup(); 
    private volatile Bootstrap bootstrap; 
 
    public void init(String host, int port) throws RobotException { 
        this.serverIp  = host; 
        this.serverPort = port; 
        try { 
            // 建立並初始化 Netty 客戶端 Bootstrap 物件 
            bootstrap = configureBootstrap(new Bootstrap(),group); 
            bootstrap.option(ChannelOption.TCP_NODELAY, true); 
            doConnect(bootstrap); 
        } 
        catch(Exception ex){ 
            ex.printStackTrace(); 
            throw new RobotException("connect remote control server error!",ex.getCause()); 
        } 
    } 
 
    Bootstrap configureBootstrap(Bootstrap b, EventLoopGroup g) { 
        b.group(g).channel(NioSocketChannel.class) 
                .remoteAddress(serverIp, serverPort) 
                .handler(new ChannelInitializer<SocketChannel>() { 
                    @Override 
                    public void initChannel(SocketChannel channel) throws Exception { 
                        ChannelPipeline pipeline = channel.pipeline(); 
                        // 編解碼器 
                        pipeline.addLast(protoCodec); 
                        // 請求處理 
                        pipeline.addLast(RobotClient.this); 
                    } 
                }); 
 
        return b; 
    } 
 
    void doConnect(Bootstrap b) { 
        try { 
 
            ChannelFuture future = b.connect(); 
            future.addListener(new ChannelFutureListener() { 
                @Override 
                public void operationComplete(ChannelFuture future) throws Exception { 
                    if (future.isSuccess()) { 
                        System.out.println("Started Tcp Client: " + serverIp); 
                    } else { 
                        System.out.println("Started Tcp Client Failed: "); 
                    } 
                    if (future.cause() != null) { 
                        future.cause().printStackTrace(); 
                    } 
 
                } 
            }); 
        } catch (Exception e) { 
            e.printStackTrace(); 
        } 
    }
 

斷線重連

來看斷線重連的關鍵程式碼：

@ChannelHandler.Sharable 
public class RobotClient extends SimpleChannelInboundHandler<RobotProto>  { 
    @Override 
    public void channelUnregistered(ChannelHandlerContext ctx) throws Exception { 
        // 狀態重置 
        isConnected = false; 
        this.serverStatus = -1; 
 
        final EventLoop loop = ctx.channel().eventLoop(); 
        loop.schedule(new Runnable() { 
            @Override 
            public void run() { 
                doConnect(configureBootstrap(new Bootstrap(), loop)); 
            } 
        }, 1, TimeUnit.SECONDS); 
    } 
}