This is from NioServerSocketChannelFactory document
A ServerSocketChannelFactory which
creates a server-side NIO-based
ServerSocketChannel. It utilizes the
non-blocking I/O mode which was
introduced with NIO to serve many
number of concurrent connections
efficiently.How threads work
There are two types
of threads in a
NioServerSocketChannelFactory; one is
boss thread and the other is worker
thread.Boss threads
Each bound
ServerSocketChannel has its own boss
thread. For example, if you opened two
server ports such as 80 and 443, you
will have two boss threads. A boss
thread accepts incoming connections
until the port is unbound. Once a
connection is accepted successfully,
the boss thread passes the accepted
Channel to one of the worker threads
that the NioServerSocketChannelFactory
manages.Worker threads
One
NioServerSocketChannelFactory can have
one or more worker threads. A worker
thread performs non-blocking read and
write for one or more Channels in a
non-blocking mode.
In Nio model, bossThread take care all bounded socket(listen socket), workerThread take care Accepted-socket (included IO and call event method such as messageReceived).