Re: intermittent connection callback exceptions

On Mon, Sep 29, 2008 at 03:37:16PM -0700, Mark Ackerman wrote:
> Out client is calling on the server to perform some work for it,
> which can take a bit of time, so we pass a callback object that the
> client has just created and exported, but no bound in the registry.
> Every so often it will throw a NullPointerException when we try and
> call on the remote object.  My customers are seeing it throw the
> exception about one in three times on their systems, and I'm seeing
> around one in seven on mine.
> 
> Exception is:
> java.lang.NullPointerException
> at sun.rmi.transport.tcp.TCPConnection.getOutputStream(TCPConnection.java:66)
> at sun.rmi.transport.tcp.TCPChannel.createConnection(TCPChannel.java:202)
> at sun.rmi.transport.tcp.TCPChannel.newConnection(TCPChannel.java:184)
> at sun.rmi.server.UnicastRef.invoke(UnicastRef.java:110)
> at hec.client.RmiProgressImpl_Stub.printStatus(Unknown Source)
> at hec.server.RmiAppImpl.openWorkspace(RmiAppImpl.java:745)
> 
> using java 1.6. client is XP and the server is Solaris.
> 
> So any ideas of where to look?  Don't see any exceptions generated
> on the client side.

The only explanation that I can think of is that a socket factory is
being used for this callback invocation, and that socket factory's
createSocket method is sometimes returning null-- which results in a
NullPointerException when the method at the top of that stack trace
attempts to invoke Socket.getOutputStream on the returned value.

-- Peter

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