Nik JainJavaJainJavaJainJava

Yes, I recompiled it several times on the new machine. I did a "Clean and build" on Netbeans and it wouldn't work. However I experimented by porting it to another machine (another another machine). Curiously, it doesn't throw the same exception there. However it wouldn't let me connect to any clients other than the localhost. Maybe firewall issues.

I started coding for a client-server machine on java, using RMI(Remote Method Invocation). The code works fine on my machine. It basically gives commands to the client machine and the client processes these commands and responds accordingly. After executing the command, the machine sends back its status to the server. An example would be, the server requests for an image feed from the client and the client returns an image to the server.

I used git to clone the current project and push it to another machine. When I execute the client side code, it works completely fine and the other machine(to which I pushed the source) responds the way it should.

However, when I run the server side code to code on the other machine, it gives a cryptic error that says:

C:\Users\RdX\Desktop\Thiswa
javax.naming.NamingException [Root exception is java.rmi.ServerError: Error occurred in server thread; nested exception is:
java.lang.UnsupportedClassVersionError: javadrone/Server (Unsupported major.minor version 51.0)]
at com.sun.jndi.rmi.registry.RegistryContext.rebind(RegistryContext.java:159)
at com.sun.jndi.toolkit.url.GenericURLContext.rebind(GenericURLContext.java:249)
at javax.naming.InitialContext.rebind(InitialContext.java:427)
at javadrone.server.ServerImpl.<init>(ServerImpl.java:46)
at javadrone.server.DroneServer.<init>(DroneServer.java:45)
at javadrone.server.DroneServer.main(DroneServer.java:84)
Caused by: java.rmi.ServerError: Error occurred in server thread; nested exception is:
java.lang.UnsupportedClassVersionError: javadrone/Server (Unsupported major.minor version 51.0)
at sun.rmi.server.UnicastServerRef.oldDispatch(UnicastServerRef.java:349)
at sun.rmi.server.UnicastServerRef.dispatch(UnicastServerRef.java:207)
at sun.rmi.transport.Transport$1.run(Transport.java:148)
at java.security.AccessController.doPrivileged(Native Method)
at sun.rmi.transport.Transport.serviceCall(Transport.java:144)
at sun.rmi.transport.tcp.TCPTransport.handleMessages(TCPTransport.java:460)
at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.run(TCPTransport.java:701)
at java.lang.Thread.run(Thread.java:534)
at sun.rmi.transport.StreamRemoteCall.exceptionReceivedFromServer(StreamRemoteCall.java:273)
at sun.rmi.transport.StreamRemoteCall.executeCall(StreamRemoteCall.java:251)
at sun.rmi.server.UnicastRef.invoke(UnicastRef.java:377)
at sun.rmi.registry.RegistryImpl_Stub.rebind(Unknown Source)
at com.sun.jndi.rmi.registry.RegistryContext.rebind(RegistryContext.java:157)
... 5 more
Caused by: java.lang.UnsupportedClassVersionError: javadrone/Server (Unsupported major.minor version 51.0)
at java.lang.ClassLoader.defineClass0(Native Method)
at java.lang.ClassLoader.defineClass(ClassLoader.java:537)
at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:123)
at java.net.URLClassLoader.defineClass(URLClassLoader.java:251)
at java.net.URLClassLoader.access$100(URLClassLoader.java:55)
at java.net.URLClassLoader$1.run(URLClassLoader.java:194)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(URLClassLoader.java:187)
at java.lang.ClassLoader.loadClass(ClassLoader.java:289)
at java.lang.ClassLoader.loadClass(ClassLoader.java:282)
at java.lang.ClassLoader.loadClass(ClassLoader.java:235)
at java.lang.ClassLoader.loadClassInternal(ClassLoader.java:302)
at java.lang.Class.forName0(Native Method)
at java.lang.Class.forName(Class.java:219)
at sun.rmi.server.LoaderHandler.loadProxyInterfaces(LoaderHandler.java:707)
at sun.rmi.server.LoaderHandler.loadProxyClass(LoaderHandler.java:651)
at sun.rmi.server.LoaderHandler.loadProxyClass(LoaderHandler.java:588)
at java.rmi.server.RMIClassLoader$2.loadProxyClass(RMIClassLoader.java:639)
at java.rmi.server.RMIClassLoader.loadProxyClass(RMIClassLoader.java:309)
at sun.rmi.server.MarshalInputStream.resolveProxyClass(MarshalInputStream.java:241)
at java.io.ObjectInputStream.readProxyDesc(ObjectInputStream.java:1469)
at java.io.ObjectInputStream.readClassDesc(ObjectInputStream.java:1432)
at java.io.ObjectInputStream.readOrdinaryObject(ObjectInputStream.java:1626)
at java.io.ObjectInputStream.readObject0(ObjectInputStream.java:1274)
at java.io.ObjectInputStream.readObject(ObjectInputStream.java:324)
at sun.rmi.registry.RegistryImpl_Skel.dispatch(Unknown Source)
at sun.rmi.server.UnicastServerRef.oldDispatch(UnicastServerRef.java:342)
at sun.rmi.server.UnicastServerRef.dispatch(UnicastServerRef.java:207)
at sun.rmi.transport.Transport$1.run(Transport.java:148)
at java.security.AccessController.doPrivileged(Native Method)
at sun.rmi.transport.Transport.serviceCall(Transport.java:144)
at sun.rmi.transport.tcp.TCPTransport.handleMessages(TCPTransport.java:460)
at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.run(TCPTransport.java:701)
at java.lang.Thread.run(Thread.java:534)

package javadrone.server; import javadrone.Drone; import javadrone.Server; import javadrone.command.CommandQueue; import java.rmi.RemoteException; import java.rmi.server.UnicastRemoteObject; import java.util.HashMap; import javax.naming.Context; import javax.naming.InitialContext; import javax.naming.NamingException; public abstract class ServerImpl extends UnicastRemoteObject implements Server { public static final String RMI_PROT = "rmi:"; private static Context namingContext; private static HashMap<String, Drone> registeredDrones; private String name; public ServerImpl(String name) throws RemoteException, NamingException { this.name = name; namingContext = new InitialContext(); namingContext.rebind(RMI_PROT + name, ServerImpl.this); registeredDrones = new HashMap<>(); } @Override public String getName() throws RemoteException { return name; } @Override public Drone registerDrone(String droneName) throws RemoteException { System.out.println("Remote client registered..."); DroneImpl d = new DroneImpl(new CommandQueue(), droneName); registeredDrones.put(droneName, d); hasRegistered(d); return d; } public Drone getDrone(String droneName) { return registeredDrones.get(droneName); } @Override public long getTime() throws RemoteException { return System.currentTimeMillis(); } public abstract void hasRegistered(DroneImpl d); }
To be specific,

namingContext.rebind(RMI_PROT + name, ServerImpl.this)
is the line that generates the error.

I searched a lot of places and they say that when the JDK compliler is of a higher version than the JRE version, it may produce such an error.

However I uninstalled all prior JDKs and JREs and recompiled the code after installing JDK 7.03. It still gives the same exception.

Why is this happening and how do I correct it?

[NK: Added code tags, UseCodeTags]