* This is useful to establish the communication with other JVMs and use them
* for different purposes outside {@link Slave}s.
* <ul>
* <li> When the <b>exists</b> method is invoked for an agent, the <b>owns</b> method is called on all the extension points: if no owner is found an exception is thrown.</li>
* <li> If owner is found, then the {@link org.jenkinsci.remoting.engine.JnlpConnectionState} lifecycle methods are invoked for all registered {@link JnlpConnectionStateListener} until the one which changes the state of {@link org.jenkinsci.remoting.engine.JnlpConnectionState} by setting an approval or rejected state is found.
* When found, that listener will be set as the owner of the incoming connection event. </li>
* <li> Subsequent steps of the connection lifecycle are only called on the {@link JnlpAgentReceiver} implementation owner for that connection event.</li>
