Hi Friends, I am seeing following exception 21-Jun-2011 18:29:01 org.apache.xmlrpc.server.XmlRpcErrorLogger log SEVERE: Failed to invoke method registerSubscriber in class org.ros.internal.node.xmlrpc.MasterImpl: null org.apache.xmlrpc.common.XmlRpcInvocationException: Failed to invoke method registerSubscriber in class org.ros.internal.node.xmlrpc.MasterImpl: null at org.apache.xmlrpc.server.ReflectiveXmlRpcHandler.invoke(ReflectiveXmlRpcHandler.java:129) at org.apache.xmlrpc.server.ReflectiveXmlRpcHandler.execute(ReflectiveXmlRpcHandler.java:106) at org.apache.xmlrpc.server.XmlRpcServerWorker.execute(XmlRpcServerWorker.java:46) at org.apache.xmlrpc.server.XmlRpcServer.execute(XmlRpcServer.java:86) at org.apache.xmlrpc.server.XmlRpcStreamServer.execute(XmlRpcStreamServer.java:200) at org.apache.xmlrpc.webserver.Connection.run(Connection.java:208) at org.apache.xmlrpc.util.ThreadPool$Poolable$1.run(ThreadPool.java:68) Caused by: java.lang.IllegalStateException at com.google.common.base.Preconditions.checkState(Preconditions.java:129) at org.ros.internal.node.server.MasterServer.addSlave(MasterServer.java:80) at org.ros.internal.node.server.MasterServer.registerSubscriber(MasterServer.java:110) at org.ros.internal.node.xmlrpc.MasterImpl.registerSubscriber(MasterImpl.java:123) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25) at java.lang.reflect.Method.invoke(Method.java:597) at org.apache.xmlrpc.server.ReflectiveXmlRpcHandler.invoke(ReflectiveXmlRpcHandler.java:115) My code is //Publisher node = new Node("Camera1", configuration); publisher = node.createPublisher("Camera1", org.ros.message.sensor_msgs.Image.class); .................... //Subscriber node = new Node("Camera1", configuration); System.out.println("ScreenView.main() Starting"); // final Log log = node.getLog(); node.createSubscriber("Camera1", new MessageListener() { public void onNewMessage(org.ros.message.sensor_msgs.Image message) { System.out .println("Subscriber \"" + message + "\""); } }, org.ros.message.sensor_msgs.Image.class); Reason behind this exception is Nodes with same name. If I change this name and create different nodes in publisher and subscribers code then its fine. Anyone has any idea why is that or we are not supposed to create node with same name? Thanks and Regards Abhishek Verma