前2篇分析了echo server端的運行機制，本篇同樣以echo client為例，分析netty的nio客戶端的運行機制。 總體來說client端和server端的處理是類似的，NioWorker是重用的，也就意味著client和server的讀寫機制是一樣的，都是通過worker線程來管理的。所不同的是Boss線程，server端的boss線程一個bind端口起一個，主要負責接收新請求，而client端的boss線程是一個可配置的數組，一個connect端口分配一個，主要負責connect過程，如果connect成功則將channle注冊到worker線程中處理。在Client同樣有PipelineSink，叫做NioClientSocketPipelineSink，也是負責底層IO和pipeline之間的交互。 EchoClient代碼: Java代碼

// 初始化Bootstrap和NioClientSocketChannelFactory，這一步將啟動nioWorker線程，并初始化NioClientSocketPipelineSink，并將Boss線程創建

ClientBootstrap bootstrap = new ClientBootstrap(

new NioClientSocketChannelFactory(

Executors.newCachedThreadPool(),

Executors.newCachedThreadPool()));

// 用戶自定義的pipeline工廠

bootstrap.setPipelineFactory(new ChannelPipelineFactory() {

public ChannelPipeline getPipeline() throws Exception {

return Channels.pipeline(

new EchoClientHandler(firstMessageSize));

}

});

// 異步創建連接

ChannelFuture future = bootstrap.connect(new InetSocketAddress(host, port));

//等待連接關閉

future.getChannel().getCloseFuture().awaitUninterruptibly();

// 關閉資源，線程池等

bootstrap.releaseExternalResources();

// 初始化Bootstrap和NioClientSocketChannelFactory，這一步將啟動nioWorker線程，并初始化NioClientSocketPipelineSink，并將Boss線程創建ClientBootstrap bootstrap = new ClientBootstrap(new NioClientSocketChannelFactory(Executors.newCachedThreadPool(),Executors.newCachedThreadPool()));// 用戶自定義的pipeline工廠bootstrap.setPipelineFactory(new ChannelPipelineFactory() {public ChannelPipeline getPipeline() throws Exception {return Channels.pipeline(new EchoClientHandler(firstMessageSize));}});// 異步創建連接ChannelFuture future = bootstrap.connect(new InetSocketAddress(host, port));//等待連接關閉future.getChannel().getCloseFuture().awaitUninterruptibly();// 關閉資源，線程池等bootstrap.releaseExternalResources(); 具體connect過程： 一.創建client的channel Java代碼

public ChannelFuture connect(final SocketAddress remoteAddress, final SocketAddress localAddress) {

......

//拿用戶自定義的pipeline

ChannelPipeline pipeline;

try {

pipeline = getPipelineFactory().getPipeline();

} catch (Exception e) {

throw new ChannelPipelineException("Failed to initialize a pipeline.", e);

}

// 從ChannelFactory中，創建Channel，對于client來說factory是NioClientSocketChannelFactory，Channel是NioClientSocketChannel

Channel ch = getFactory().newChannel(pipeline);

// 通過channel連接

return ch.connect(remoteAddress);

}

public ChannelFuture connect(final SocketAddress remoteAddress, final SocketAddress localAddress) {......//拿用戶自定義的pipelineChannelPipeline pipeline;try {pipeline = getPipelineFactory().getPipeline();} catch (Exception e) {throw new ChannelPipelineException("Failed to initialize a pipeline.", e);}// 從ChannelFactory中，創建Channel，對于client來說factory是NioClientSocketChannelFactory，Channel是NioClientSocketChannelChannel ch = getFactory().newChannel(pipeline);// 通過channel連接return ch.connect(remoteAddress);} 二.創建channel時，分配worker Java代碼

public SocketChannel newChannel(ChannelPipeline pipeline) {

return new NioClientSocketChannel(this, pipeline, sink, sink.nextWorker());

}

public SocketChannel newChannel(ChannelPipeline pipeline) {return new NioClientSocketChannel(this, pipeline, sink, sink.nextWorker());} 三.創建內部的SocketChannel，觸發ChannelOpen事件，不過echo client的handler沒有對channelOpen事件做處理

轉載于:https://blog.51cto.com/daheyuan/1140093

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