It seems there is an issue with the Netty ipc mechanism. It's closing it's connection after the first invocation and all subsequent invocations fail.
The other IPC mechanisms store the negotiated protocol in the Tranceiver and use this to indicate if the connection should be maintained. The patch adds this functionality to the Netty Server; it now passes in a tranceiver for this purpose and only closes the connection if the 'isConnected' call after the response is false.
The patch tweaks the tests a little too, adding a test for the number of handshakes and adding a repeated calls test to catch this in the future.