HornetQ User Guide - chapter 14.4.1. Configuring Netty TCP

Change:
use-nio
If true, NIO is used. If false, AIO is used. T he default is false on both client and server
sides. If your server must handle many concurrent connections, NIO is recommended, since it
does not maintain one thread per connection and can scale to many more concurrent
connections than AIO. If your server does not need to handle many concurrent connections, AIO
may provide better performance.

To:
use-nio
If this is true then Java non blocking NIO will be used. If set to false then old blocking Java IO will be used.
If you require the server to handle many concurrent connections, we highly recommend that you use non blocking Java NIO. Java NIO does not maintain a thread per connection so can scale to many more concurrent connections than with old blocking IO. If you don't require the server to handle many concurrent connections, you might get slightly better performance by using old (blocking) IO. The default value for this property is false on the server side and false on the client side.

Thanks,

Mirek