Java RMI Client access denied

javarmi

I have a small Java RMI Server and Client program I'm writing. I have spent some time trying to figure out the error messages without success.

The Client generates the following error:

Trying to connect to: 127.0.0.1:3232
ERROR!!!: StockClient: main: Could not connect to the server: java.rmi.UnmarshalException: Error unmarshaling return header; nested
exception is:
java.rmi.UnmarshalException: Error unmarshaling return header; nested exception is:
java.io.EOFException
java.io.EOFException
at sun.rmi.transport.StreamRemoteCall.executeCall(StreamRemoteCall.java:209)
at sun.rmi.server.UnicastRef.invoke(UnicastRef.java:359)
at sun.rmi.registry.RegistryImpl_Stub.lookup(Unknown Source)
at StockClient.StockClient.main(StockClient.java:44)
Caused by: java.io.EOFException
at java.io.DataInputStream.readByte(DataInputStream.java:250)
at sun.rmi.transport.StreamRemoteCall.executeCall(StreamRemoteCall.java:195)
… 3 more

With the server the following error only when the client attempts to connect.

this address=localhost/127.0.0.1,port=3232
Exception in thread "RMI TCP Connection(idle)" java.security.AccessControlException: access denied
(java.net.SocketPermission 127.0.0.1:62586 accept,resolve)
at java.security.AccessControlContext.checkPermission(AccessControlContext.java:374)
at java.security.AccessController.checkPermission(AccessController.java:549)
at java.lang.SecurityManager.checkPermission(SecurityManager.java:532)
at java.lang.SecurityManager.checkAccept(SecurityManager.java:1157)
at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.checkAcceptPermission(TCPTransport.java:636)
at sun.rmi.transport.tcp.TCPTransport.checkAcceptPermission(TCPTransport.java:275)
at sun.rmi.transport.Transport$1.run(Transport.java:158)
at java.security.AccessController.doPrivileged(Native Method)
at sun.rmi.transport.Transport.serviceCall(Transport.java:155)
at sun.rmi.transport.tcp.TCPTransport.handleMessages(TCPTransport.java:535)
at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.run0(TCPTransport.java:790)
at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.run(TCPTransport.java:649)
at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908)
at java.lang.Thread.run(Thread.java:680)

Because of the server error I'm fairly sure its a security or registry error, security policy for the server is:

grant {
permission java.security.AllPermission;
};

and being run with the following argument

-Djava.security.policy=client.policy

I've tried everything I can find but seem to keep going around in circles.

relevant methods:

Server:

 public static void main(String[] args)
    {//main(...) starts
        // set up the data structures and data

        //add users
        //Users hard coded as this is an example proof on concept program
        //Names and passwords not hashed for simplicity
        User alpha = new User("Alpha", "AlphaPass");
        User omega = new User("Omega", "OmegaPass");
        users.add(alpha);
        users.add(omega);

        //startup the RMI server
        try
        {
            System.setSecurityManager(new RMISecurityManager());
            StockServer server = new StockServer();
            StockServerInterface inter = (StockServerInterface)
UnicastRemoteObject.exportObject (server,0);

            // create the registry and bind the name and object.
            registry = LocateRegistry.createRegistry(thisPort);
            registry.rebind("StockServer", inter);
        }
        catch (Exception e)
        {
            System.out.println("Unable to create StockServer: " + e);
            e.printStackTrace();
            System.exit(1);
        }
    }//main(...) ends


    /**
     * Constructor for StockServer
     *
     * @throws RemoteException
     */
    public StockServer() throws RemoteException
    {

        //try to get the host machine's IP address
        try
        {
            // get the address of this host.
            thisAddress = (InetAddress.getLocalHost()).toString();
        } catch (Exception e)
        {
            throw new RemoteException("can't get inet address. " + e);
        }

        //Set the port
        thisPort = 3232;

        //Print out the server address and port
        System.out.println("this address=" + thisAddress + ",port=" + thisPort);
    }

Client:

private static StockServerInterface stockServer;
static public void main(String args[])
{
    Registry registry;
    //get the server address from the args
    String serverAddress = args[0];

    //get the server port from the args
    String serverPort = args[1];

    //Let the user know we are about to try to connect
    System.out.println("Trying to connect to: " + serverAddress + ":" + serverPort);
    try
    {
        // get the registry
        registry = LocateRegistry.getRegistry(
                serverAddress,
                (new Integer(serverPort)).intValue());
        // look up the remote object
        stockServer = (StockServerInterface) (registry.lookup("StockServer"));


        //Authenticate the user
        authenticate();

        //setup the hashset
        HashSet<Stock> hashStockSet = null;

        //setup the hashset of desired stocks
        try
        {
            hashStockSet = getHashSet();
        } catch (IOException e)
        {
            e.printStackTrace();
            System.exit(1);
        } catch (ClassNotFoundException e)
        {
            e.printStackTrace();
            System.exit(1);
        }
        //bit of a heavy handed infinte loop so we continue to get the loop
        while(true)
        {
            //Run the ticker
            ticker(hashStockSet);
        }

        // call the remote method


    }
    catch (RemoteException e)
    {
        System.out.println("ERROR!!!: StockClient: main: Could not connect to the server: "+e);
        e.printStackTrace();
    }
    catch (NotBoundException e)
    {
        System.out.println("ERROR!!!: StockClient: main: Could not connect to the server: "+e);
        e.printStackTrace();
    }

Best Answer

You don't need a SecurityManager in an RMI server unless the client is relying on the codebase feature to supply the server with classes. Either remove it, or debug the .policy file. Clearly the one you've written isn't being loaded.

Run your server with -Djava.security.debug=access,failure and you will see where all the security domains are getting their configurations from, and the domain that is failing at the point where the exception is thrown.

Related Solutions

Java – What are the differences between a HashMap and a Hashtable in Java

There are several differences between HashMap and Hashtable in Java:

Hashtable is synchronized, whereas HashMap is not. This makes HashMap better for non-threaded applications, as unsynchronized Objects typically perform better than synchronized ones.
Hashtable does not allow null keys or values. HashMap allows one null key and any number of null values.
One of HashMap's subclasses is LinkedHashMap, so in the event that you'd want predictable iteration order (which is insertion order by default), you could easily swap out the HashMap for a LinkedHashMap. This wouldn't be as easy if you were using Hashtable.

Since synchronization is not an issue for you, I'd recommend HashMap. If synchronization becomes an issue, you may also look at ConcurrentHashMap.

Java – Is Java “pass-by-reference” or “pass-by-value”

Java is always pass-by-value. Unfortunately, when we deal with objects we are really dealing with object-handles called references which are passed-by-value as well. This terminology and semantics easily confuse many beginners.

It goes like this:

public static void main(String[] args) {
    Dog aDog = new Dog("Max");
    Dog oldDog = aDog;

    // we pass the object to foo
    foo(aDog);
    // aDog variable is still pointing to the "Max" dog when foo(...) returns
    aDog.getName().equals("Max"); // true
    aDog.getName().equals("Fifi"); // false
    aDog == oldDog; // true
}

public static void foo(Dog d) {
    d.getName().equals("Max"); // true
    // change d inside of foo() to point to a new Dog instance "Fifi"
    d = new Dog("Fifi");
    d.getName().equals("Fifi"); // true
}

In the example above aDog.getName() will still return "Max". The value aDog within main is not changed in the function foo with the Dog "Fifi" as the object reference is passed by value. If it were passed by reference, then the aDog.getName() in main would return "Fifi" after the call to foo.

Likewise:

public static void main(String[] args) {
    Dog aDog = new Dog("Max");
    Dog oldDog = aDog;

    foo(aDog);
    // when foo(...) returns, the name of the dog has been changed to "Fifi"
    aDog.getName().equals("Fifi"); // true
    // but it is still the same dog:
    aDog == oldDog; // true
}

public static void foo(Dog d) {
    d.getName().equals("Max"); // true
    // this changes the name of d to be "Fifi"
    d.setName("Fifi");
}

In the above example, Fifi is the dog's name after call to foo(aDog) because the object's name was set inside of foo(...). Any operations that foo performs on d are such that, for all practical purposes, they are performed on aDog, but it is not possible to change the value of the variable aDog itself.

For more information on pass by reference and pass by value, consult the following SO answer: https://stackoverflow.com/a/430958/6005228. This explains more thoroughly the semantics and history behind the two and also explains why Java and many other modern languages appear to do both in certain cases.

Best Answer

Related Solutions

Java – What are the differences between a HashMap and a Hashtable in Java

Java – Is Java “pass-by-reference” or “pass-by-value”

Related Topic