Transport API的核心：

Channel接口

类图表示Channel含有Pipeline和Config接口，pipeline上一节有所介绍。

Channel是线程安全的，这表示在多线环境下操作同一个Channel，不会有数据问题。

final Channel channel = null;
		final ByteBuf buf = Unpooled.copiedBuffer("your data",
				CharsetUtil.UTF_8); // #1
		Runnable writer = new Runnable() { // #2
			@Override
			public void run() {
				channel.write(buf.duplicate());
			}
		};
		Executor executor = Executors.newCachedThreadPool(); // #3
		// write in one thread
		executor.execute(writer); // #4
		// write in another thread
		executor.execute(writer); // #5
 
#1 Create ByteBuf that holds data to write
#2 Create Runnable which writes data to channel
#3 Obtain reference to the Executor which uses threads to execute tasks
#4 Hand over write task to executor for execution in thread
#5 Hand over another write task to executor for execution in thread

This method guarantees that the messages are written in the same order as you passed them to the write method.（这个方法保证信息被写入到Channel中的顺序和调用write方法的顺序是一致的。）

Transports:

每个传输方式都有对应的EventLoop:

最后一个ThreadPerChannelEventLoop就是OIO（Old-IO）的事件监听器。

NIO – Nonblocking I/O:

Embedded transport：