I start remotely a JDBC test as described in the user manual (7. Building a 
Database Test Plan)

The necessary steps as described in 
http://jakarta.apache.org/jmeter/usermanual/remote-test.html are performed ; 
including starting up the rmiregistry.

But I get no results back from the remote jmeter server. I do notice a 
NullPointer exception logged on this remote system.

When debugging this remote jmeter server, I remark that the transient private 
member, namely ‘manager’ is null for the JDCSSampler where testEnded() is 
called up on. This identifies the cause of the NullPointer exception.

    public synchronized void testEnded()
    {
    	log.debug("testEndded(), thread: "+Thread.currentThread().getName());
    	manager.shutdown();
    	dbkey = null;
    }

This JDBCSampler is involved in clone :
TreeCloner.addNode(Object, HashTree) line: 64
ListedHashTree(HashTree).traverseInto(HashTreeTraverser) line: 1006
ListedHashTree(HashTree).traverse(HashTreeTraverser) line: 985
StandardJMeterEngine.cloneTree(ListedHashTree) line: 178
StandardJMeterEngine.run() line: 303
Thread.run() line: 534 [local variables unavailable]
But there the private member manager is already null.

JDBCSampler is also derived from Serializable. So must the following method 
also not be implemented ?
private void writeObject(java.io.ObjectOutputStream out) throws IOException

Kind regards
Johan