Ice.NoEndpointException when any node not start

Hi,
I use IceJ-3.1.0/demo/IceGrid/simple and add two nodes to application ,if any one node not start ,will get a NoEndpointException , how can I do?

Thanks

[root@svr149 simple]# java Client
Client: Ice.NoEndpointException
proxy = "hello -t"
Ice.NoEndpointException
proxy = "hello -t"
at IceInternal.RoutableReference.createConnection(RoutableReference.java:364)
at IceInternal.IndirectReference.getConnection(IndirectReference.java:175)
at Ice._ObjectDelM.setup(_ObjectDelM.java:258)
at Ice.ObjectPrxHelperBase.__getDelegate(ObjectPrxHelperBase.java:905)
at Ice.ObjectPrxHelperBase.ice_isA(ObjectPrxHelperBase.java:73)
at Ice.ObjectPrxHelperBase.ice_isA(ObjectPrxHelperBase.java:61)
at Demo.HelloPrxHelper.checkedCast(HelloPrxHelper.java:90)
at Client.run(Client.java:36)
at Ice.Application.main(Application.java:114)
at Ice.Application.main(Application.java:57)
at Client.main(Client.java:106)





<icegrid>

<application name="Simple">

<server-template id="SimpleServer">
<parameter name="index"/>
<server id="SimpleServer-${index}" exe="java" activation="on-demand">
<option>Server</option>
<adapter name="Hello" endpoints="tcp" register-process="true" replica-group="ReplicatedHelloAdapter"/>
<property name="Identity" value="hello"/>
</server>
</server-template>

<replica-group id="ReplicatedHelloAdapter">
<load-balancing type="round-robin"/>
<object identity="hello" type="::Demo::Hello"/>
</replica-group>

<node name="n1">
<server-instance template="SimpleServer" index="1"/>
</node>

<node name="n2">
<server-instance template="SimpleServer" index="2"/>
</node>


</application>

</icegrid>