Netty 5.0.0.Alpha4 Released with API Cleanup and Unix Domain Socket Support

Netty 5.0.0.Alpha4 has been released, eliminating a large amount of duplicated code and cleaning up the API. In addition, it adds support for Unix Domain Socket when using the JDK NIO implementation.

Main Changes

Support creating all SocketChannel and DatagramChannel implementations that include ProtocolFamily. The ProtocolFamily influences decisions such as whether to use Unix Domain Socket and also allows removal of Domain*Channel implementations for consistency.

Rename ChannelOption.RECVBUF_ALLOCATOR to RECVBUFFER_ALLOCATOR.

Support JDK's Unix Domain Socket.

Change EventLoop / IoHandler to take / IoHandle for registration, enabling future registration of entities other than Channels to an EventLoop.

Clean up RecvBufferAllocator.

Fix the disconnect() implementation in the macOS native implementation.

Replace synchronized with Java Locks to better support Loom.

To allow developers to try Netty 5 while still using 4.1, the team placed the two versions in different packages so they can coexist. Because this is a new major version, it includes many breaking changes, largely informed by lessons learned from the Netty 4.1.x lifecycle.

The default branch of Netty will be switched to main, making the changes acceptable to the 4.1 line stricter to minimize the chance of rolling back to 4.1. Important bug fixes will still be back‑ported to 4.1. Consequently, the team does not plan to stop supporting 4.1.x; both Netty 5 and 4.1.x will be maintained simultaneously.