HornetQ is using Netty 3 with OIO, which is using BlockedIO, which is basically an SocketOutputStream.
There is an issue with disconnecting the cable or disabling network, in which the writer will lock the Pinger, Pinger will not be able to cleanup the connection.

Notice this not apply to Artemis which is 100 non blocking, so I'm not sure these fixes will be applied upstream in Artemis.

Version-Release number of selected component (if applicable):

How reproducible:
100% reproduceable.

Steps to Reproduce:
1. Have a producer connection so much that it flow control the server. (disable flow control for easier reproducing)
2. Disconnect network (ifconfig down or pull of cable)

or:

1. I have developed NettyManualFailoverTest which will be part of the fix. follow the steps of the test and it will show the issue.