Netty之writeAndFlush()流程

整体步骤：先write再flush

write流程

ctx.writeAndFlush() –> TailHandler –> Handler … —> HeadHandler –> Unsafe.write()
write方法实际上并没有将消息写出去, 而是将消息msg和此次操作的promise放入到当前连接的输出缓冲区OutboundBuffer中了；

flush流程

ctx.writeAndFlush() –> TailHandler –> Handler … —> HeadHandler –> Unsafe.flush() –> AbstractNioByteChannel.doWrite() –> ChannelOutboundBuffer.remove() –> Promise.notifyListeners();