NOTE
Netty 3.x Source Analysis (Historical)
Historical Netty 3 architecture and why its APIs/classes should not be projected onto modern Netty 4.x designs.
This is a historical learning note and may contain outdated or incomplete understanding.
This note belongs to Netty 3.x and should be read as historical architecture context.
Netty 4 substantially redesigned important APIs around event loops, channels/pipelines, futures, and especially buffer/reference-counting abstractions. Class names and source call paths from 3.x are therefore not reliable descriptions of modern Netty.
The transferable ideas are event-driven networking, channel pipelines, asynchronous completion, and avoiding one blocking thread per connection—not the exact 3.x implementation.