During intensive HA-JNDI failover testing (constantly running "new InitialContext().lookup(...)"
while starting and stopping JBoss instances, sometimes an HA-JNDI lookup just before the server goes down is
throwing an exception without trying to fail over to the other HA-JNDI instance:

...
Caused by: javax.naming.CommunicationException [Root exception is java.rmi.UnmarshalException: Error unmarshaling return header; nested exception is:
java.net.SocketException: Connection reset]
at org.jnp.interfaces.NamingContext.lookup(NamingContext.java:863)
at org.jnp.interfaces.NamingContext.lookup(NamingContext.java:710)
at javax.naming.InitialContext.lookup(InitialContext.java:351)
at xxx.CustomCode (CustomCode.java:XXX)
... 25 more
Caused by: java.rmi.UnmarshalException: Error unmarshaling return header; nested exception is:
java.net.SocketException: Connection reset
at sun.rmi.transport.StreamRemoteCall.executeCall(StreamRemoteCall.java:203)
at sun.rmi.server.UnicastRef.invoke(UnicastRef.java:126)
at org.jboss.ha.framework.server.HARMIServerImpl_Stub.invoke(Unknown Source)
at org.jboss.ha.framework.interfaces.HARMIClient.invokeRemote(HARMIClient.java:225)
at org.jboss.ha.framework.interfaces.HARMIClient.invoke(HARMIClient.java:327)
at $Proxy4.lookup(Unknown Source)
at org.jnp.interfaces.NamingContext.lookup(NamingContext.java:750)
... 28 more
Caused by: java.net.SocketException: Connection reset
at java.net.SocketInputStream.read(SocketInputStream.java:168)
at java.io.BufferedInputStream.fill(BufferedInputStream.java:218)
at java.io.BufferedInputStream.read(BufferedInputStream.java:235)
at java.io.DataInputStream.readByte(DataInputStream.java:241)
at sun.rmi.transport.StreamRemoteCall.executeCall(StreamRemoteCall.java:189)
... 34 more

Also a similar exception:
Caused by: java.net.SocketException: socket write error: Connection reset by peer.
at jrockit.net.SocketNativeIO.writeBytesPinned(Native Method)
at jrockit.net.SocketNativeIO.socketWrite(SocketNativeIO.java:73)
at java.net.SocketOutputStream.socketWrite0(SocketOutputStream.java)
at java.net.SocketOutputStream.socketWrite(SocketOutputStream.java:92)
at java.net.SocketOutputStream.write(SocketOutputStream.java:137)
at java.io.BufferedOutputStream.flushBuffer(BufferedOutputStream.java:65)
at java.io.BufferedOutputStream.flush(BufferedOutputStream.java:123)
at java.io.ObjectOutputStream$BlockDataOutputStream.flush(ObjectOutputStream.java:1632)
at java.io.ObjectOutputStream.flush(ObjectOutputStream.java:667)
at sun.rmi.transport.StreamRemoteCall.releaseOutputStream(StreamRemoteCall.java:92)
at sun.rmi.transport.StreamRemoteCall.executeCall(StreamRemoteCall.java:188)
at sun.rmi.server.UnicastRef.invoke(UnicastRef.java:126)
at org.jboss.ha.framework.server.HARMIServerImpl_Stub.invoke(Unknown Source)
at org.jboss.ha.framework.interfaces.HARMIClient.invokeRemote(HARMIClient.java:225)
at org.jboss.ha.framework.interfaces.HARMIClient.invoke(HARMIClient.java:327)
at $Proxy4.lookup(Unknown Source)
at org.jnp.interfaces.NamingContext.lookup(NamingContext.java:750)
at org.jnp.interfaces.NamingContext.lookup(NamingContext.java:710)
at javax.naming.InitialContext.lookup(InitialContext.java:351)
...

Also
javax.naming.CommunicationException [Root exception is java.rmi.UnmarshalException: Error unmarshaling return header; nested exception is:
java.io.EOFException]
...

Root cause is that java.rmi.UnmarshallException is not caught as an exception eligible for failover.