Netty断线重连

Netty断线重连

最近使用Netty开发一个中转服务，需要一直保持与Server端的连接，网络中断后需要可以自动重连，查询官网资料，实现方案很简单，核心思想是在channelUnregistered钩子函数里执行重连。

创建连接#

需要把configureBootstrap重构为一个函数，方便后续复用

1. EventLoopGroup group = new NioEventLoopGroup(); 

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2. private volatile Bootstrap bootstrap; 

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3.  

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4. public void init(String host, int port) throws RobotException { 

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5. this.serverIp = host; 

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6. this.serverPort = port; 

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7. try { 

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8. // 创建并初始化 Netty 客户端 Bootstrap 对象 

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9. bootstrap = configureBootstrap(new Bootstrap(),group); 

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10. bootstrap.option(ChannelOption.TCP_NODELAY, true); 

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11. doConnect(bootstrap); 

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12. } 

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13. catch(Exception ex){ 

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14. ex.printStackTrace(); 

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15. throw new RobotException("connect remote control server error!",ex.getCause()); 

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16. } 

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17. } 

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18.  

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19. Bootstrap configureBootstrap(Bootstrap b, EventLoopGroup g) { 

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20. b.group(g).channel(NioSocketChannel.class) 

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21. .remoteAddress(serverIp, serverPort) 

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22. .handler(new ChannelInitializer<SocketChannel>() { 

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23. @Override 

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24. public void initChannel(SocketChannel channel) throws Exception { 

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25. ChannelPipeline pipeline = channel.pipeline(); 

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26. // 编解码器 

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27. pipeline.addLast(protoCodec); 

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28. // 请求处理 

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29. pipeline.addLast(RobotClient.this); 

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30. } 

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31. }); 

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32.  

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33. return b; 

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34. } 

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35.  

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36. void doConnect(Bootstrap b) { 

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37. try { 

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38.  

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39. ChannelFuture future = b.connect(); 

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40. future.addListener(new ChannelFutureListener() { 

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41. @Override 

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42. public void operationComplete(ChannelFuture future) throws Exception { 

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43. if (future.isSuccess()) { 

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44. System.out.println("Started Tcp Client: " + serverIp); 

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45. } else { 

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46. System.out.println("Started Tcp Client Failed: "); 

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47. } 

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48. if (future.cause() != null) { 

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49. future.cause().printStackTrace(); 

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50. } 

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51.  

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52. } 

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53. }); 

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54. } catch (Exception e) { 

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55. e.printStackTrace(); 

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56. } 

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57. } 

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断线重连#

来看断线重连的关键代码：

1. @ChannelHandler.Sharable 

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2. public class RobotClient extends SimpleChannelInboundHandler<RobotProto> { 

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3. @Override 

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4. public void channelUnregistered(ChannelHandlerContext ctx) throws Exception { 

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5. // 状态重置 

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6. isConnected = false; 

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7. this.serverStatus = -1; 

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8.  

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9. final EventLoop loop = ctx.channel().eventLoop(); 

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10. loop.schedule(new Runnable() { 

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11. @Override 

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12. public void run() { 

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13. doConnect(configureBootstrap(new Bootstrap(), loop)); 

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14. } 

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15. }, 1, TimeUnit.SECONDS); 

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16. } 

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17. } 

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需要注意，Client类需要添加@ChannelHandler.Sharable注解，否则重连时会报错

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作者：Jadepeng
出处：jqpeng的技术记事本--http://www.cnblogs.com/xiaoqi
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