README.md

Option

ChannelOption.SO_BACKLOG: the maximum queue length for incoming connection indications(a request to connect) is set to the backlog parameter. If a connection indication arrives when the queue is full, the connection is refused.

option vs childOption:

stackoverflow

1.

The parameters that we set using ServerBootStrap.option apply to the ChannelConfig of a newly created ServerChannel,i.e., the server socket which listens for and accepts the client connections. These options will be set on the Server Channel when bind() or connect() method is called. This channel is one per server.

2.

The ServerBootStrap.childOption applies to a channel's channelConfig which gets created once the serverChannel accepts a client connection. This channel is per client(or per client socket)

3.

So ServerBootStrap.option parameters apply to the server socket(Server channel) that is listening for connections and ServerBootStrap.childOption parameters apply to the socket that gets created once the connection is accepted by the server socket.