Develop Reference

Rmi getDate() Program gives error at client side

I am trying to write an RMI code for the very first time. The program performs a very simple function of getting the date from the server. I somehow managed to get the server running however at the client side exceptions occur:
Exception in thread "main" java.rmi.NotBoundException: //localhost/RemoteDatum
at sun.rmi.registry.RegistryImpl.lookup(RegistryImpl.java:166)
at sun.rmi.registry.RegistryImpl_Skel.dispatch(Unknown Source)
at sun.rmi.server.UnicastServerRef.oldDispatch(UnicastServerRef.java:410)
at sun.rmi.server.UnicastServerRef.dispatch(UnicastServerRef.java:268)
at sun.rmi.transport.Transport$1.run(Transport.java:200)
at sun.rmi.transport.Transport$1.run(Transport.java:197)
at java.security.AccessController.doPrivileged(Native Method)
at sun.rmi.transport.Transport.serviceCall(Transport.java:196)
at sun.rmi.transport.tcp.TCPTransport.handleMessages(TCPTransport.java:568)
at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.run0(TCPTransport.java:826)
at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.lambda$run$254(TCPTransport.java:683)
at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler$$Lambda$1/1287360293.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.run(TCPTransport.java:682)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
at java.lang.Thread.run(Thread.java:745)
at sun.rmi.transport.StreamRemoteCall.exceptionReceivedFromServer(StreamRemoteCall.java:276)
at sun.rmi.transport.StreamRemoteCall.executeCall(StreamRemoteCall.java:253)
at sun.rmi.server.UnicastRef.invoke(UnicastRef.java:379)
at sun.rmi.registry.RegistryImpl_Stub.lookup(Unknown Source)
at MyClient.main(MyClient.java:15)
My Interface "RemoteDatum" looks like this: (I copied the interface in server to the client Project folder and the stubs were generated by the RMI eclipse plugin)
import java.rmi.Remote;
import java.rmi.RemoteException;
import java.util.Date;
public interface RemoteDatum extends Remote{
public Date holeDatum() throws RemoteException; //holeDatum means getDate in german
}
RemoteDatumImpl: Implementation of Interface
import java.rmi.RemoteException;
import java.rmi.server.UnicastRemoteObject;
import java.util.Date;
public class RemoteDatumImpl extends UnicastRemoteObject implements RemoteDatum {
protected RemoteDatumImpl() throws RemoteException {
super();
}
public Date holeDatum() throws RemoteException
{
return new Date();
}
}
The server:
import java.net.MalformedURLException;
import java.rmi.Naming;
import java.rmi.Remote;
import java.rmi.RemoteException;
import java.rmi.registry.LocateRegistry;
import java.rmi.registry.Registry;
import java.rmi.server.UnicastRemoteObject;
public class MyServer extends UnicastRemoteObject {
protected MyServer() throws RemoteException {
super();
}
public static void main(String[] args) throws RemoteException, MalformedURLException
{
try
{
String name = "RemoteDatum";
Registry r = LocateRegistry.getRegistry();
MyServer service = new MyServer();
r.rebind(name, service);
}catch(Exception ex){ex.printStackTrace();}
}
}
My Client:
import java.net.MalformedURLException;
import java.rmi.NotBoundException;
import java.rmi.RemoteException;
import java.rmi.registry.LocateRegistry;
import java.rmi.registry.Registry;
public class MyClient {
public static void main(String[] args) throws RemoteException, MalformedURLException, NotBoundException
{
Registry r = LocateRegistry.getRegistry();
String name = "//localhost/RemoteDatum";
RemoteDatum service = (RemoteDatum) r.lookup(name);
System.out.println(service.holeDatum());
}
}
I am using Eclipse RMI plugin to start RMI registry and don't know if that is relevant. I am using a Mac.

First:
Registry r = LocateRegistry.getRegistry();
Unless the client is running on the same host as the server, you need to get the server's Registry, not your own:
Registry r = LocateRegistry.getRegistry("serverhost);
Then:
String name = "//localhost/RemoteDatum";
RemoteDatum service = (RemoteDatum) r.lookup(name);
If you're using the Registry interface, you should not include the hostname in the lookup string. It should just be "RemoteDatum".
Alternatively, if you using the Naming class, you should include the hostname:
RemoteDatum service = (RemoteDatum)Naming.lookup("//serverhost/RemoteDatum");

SignalR java cannot connect to server

I'm having trouble connecting my java application to my SignalR Server.
The server is very simple and can be found here:
https://code.msdn.microsoft.com/windowsdesktop/Using-SignalR-in-WinForms-f1ec847b
I can connect web clients(javascript) and windows clients (C#) but I'm having trouble with my java client.(https://github.com/SignalR/java-client)
Here is my code so far:
package javaapplication2;
import java.io.IOException;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.TimeoutException;
import microsoft.aspnet.signalr.client.SignalRFuture;
import microsoft.aspnet.signalr.client.hubs.HubConnection;
import microsoft.aspnet.signalr.client.hubs.HubProxy;
public class JavaApplication2 {
public static void main(String[] args) throws IOException, InterruptedException, ExecutionException, TimeoutException
{
String ServerURI = "http://localhost:8080/signalr";
HubConnection Connection = new HubConnection(ServerURI);
HubProxy HubProxy = Connection.createHubProxy("MyHub");
HubProxy.on("AddMessage", () -> { System.out.println("Some message"); });
Connection.error(new ErrorCallback() {
#Override
public void onError(Throwable error) {
error.printStackTrace(); //<==SocketException
}
});
SignalRFuture<Void> con =Connection.start();
con.get();
}
}
Update
When I run it I get a "ExecutionException: java.net.SocketException: Connection reset"
Exception in thread "main" java.util.concurrent.ExecutionException: java.net.SocketException: Connection reset
at microsoft.aspnet.signalr.client.SignalRFuture.get(SignalRFuture.java:112)
at microsoft.aspnet.signalr.client.SignalRFuture.get(SignalRFuture.java:102)
at javaapplication2.JavaApplication2.main(JavaApplication2.java:27)
Caused by: java.net.SocketException: Connection reset
at java.net.SocketInputStream.read(SocketInputStream.java:209)
at java.net.SocketInputStream.read(SocketInputStream.java:141)
at java.io.BufferedInputStream.fill(BufferedInputStream.java:246)
at java.io.BufferedInputStream.read1(BufferedInputStream.java:286)
at java.io.BufferedInputStream.read(BufferedInputStream.java:345)
at sun.net.www.http.HttpClient.parseHTTPHeader(HttpClient.java:704)
at sun.net.www.http.HttpClient.parseHTTP(HttpClient.java:647)
at sun.net.www.http.HttpClient.parseHTTP(HttpClient.java:675)
at sun.net.www.protocol.http.HttpURLConnection.getInputStream0(HttpURLConnection.java:1535)
at sun.net.www.protocol.http.HttpURLConnection.getInputStream(HttpURLConnection.java:1440)
at java.net.HttpURLConnection.getResponseCode(HttpURLConnection.java:480)
at microsoft.aspnet.signalr.client.http.java.NetworkRunnable.run(NetworkRunnable.java:72)
at java.lang.Thread.run(Thread.java:745)
-If I change "localhost" to something that does not exist ( e.g locahostX) I get a java.net.UnknownHostException
-If If change "localhost" to my IP I don't event get an exception...
-All the other apps work with both (localhost or IP)
At first I thought it was a firewall issue but it wasn't that...
Obviously I'm missing something...
Any ideas?
Thanks

It turns out that I had to use an overload of start,the one that takes as a parameter a ClientTransport object
public SignalRFuture<Void> start(ClientTransport transport)
If anyone has an explanation why the parameterless start method fails ,please post it as an answer and I will mark it as the solution.
Here is a full example that works:
package javaapplication2;
import java.io.IOException;
import java.util.Scanner;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.TimeoutException;
import microsoft.aspnet.signalr.client.SignalRFuture;
import microsoft.aspnet.signalr.client.hubs.HubConnection;
import microsoft.aspnet.signalr.client.hubs.HubProxy;
import microsoft.aspnet.signalr.client.transport.ServerSentEventsTransport;
import microsoft.aspnet.signalr.client.hubs.SubscriptionHandler2;
public class JavaApplication2 {
public static void main(String[] args) throws IOException, InterruptedException, ExecutionException, TimeoutException
{
String ServerURI = "http://localhost:8080/signalr";
HubConnection Connection = new HubConnection(ServerURI);
HubProxy HubProxy = Connection.createHubProxy("MyHub");
HubProxy.on("AddMessage", new SubscriptionHandler2<String, String>() {
#Override
public void run(String e1, String e2) {
System.out.println(e1.toString()+ " -> " +e2.toString());
}
}, String.class, String.class);
SignalRFuture<Void> con =Connection.start(new ServerSentEventsTransport(Connection.getLogger())); //Or LongPollingTransport
con.get();
Scanner inputReader = new Scanner(System.in);
String line = inputReader.nextLine();
while (!"exit".equals(line)) {
HubProxy.invoke("send", "Console", line);
line = inputReader.next();
}
inputReader.close();
Connection.stop();
}
}

If I change "localhost" to something that does not exist ( e.g
locahostX) I get a java.net.UnknownHostException
Are you sure about this?
On the server command prompt run "ipconfig" to get the IP address of the server.
From the client command prompt type "ping " + IP address of the server.
If the ping sends packages, then try to put the IP in the string "ServerURI" to be something like "http://"+ServerIP+":8080/signalr".

websocket was forcibly closed by the remote host

hi guys im trying implement an example of send file through websocket using sendBinary method . I`m deploying server code in Tomcat 8.0.20 and client code using tyrus 1.8.3 implementation/provider . There are my server and client class :
Server code :
package socket;
import java.io.IOException;
import java.nio.ByteBuffer;
import javax.websocket.CloseReason;
import javax.websocket.OnClose;
import javax.websocket.OnError;
import javax.websocket.OnMessage;
import javax.websocket.OnOpen;
import javax.websocket.Session;
import javax.websocket.server.ServerEndpoint;
#ServerEndpoint("/chat")
public class Server {
#OnOpen
public void onOpen(Session session) {
}
#OnClose
public void onClose(Session session,CloseReason closeReason) {
}
#OnError
public void onError(Throwable throwable){
throwable.printStackTrace();
}
#OnMessage
public void message(String message, Session session) throws IOException {
}
#OnMessage
public void message(Session session,ByteBuffer byteBuffer) throws IOException {
System.out.println(" Binary received ... ");
}
}
Client code :
package br.com.jslsolucoes.socket.client;
import java.io.IOException;
import java.io.InputStream;
import java.net.URI;
import java.nio.ByteBuffer;
import java.util.concurrent.CountDownLatch;
import javax.websocket.ClientEndpoint;
import javax.websocket.CloseReason;
import javax.websocket.ContainerProvider;
import javax.websocket.DeploymentException;
import javax.websocket.OnClose;
import javax.websocket.OnError;
import javax.websocket.OnMessage;
import javax.websocket.OnOpen;
import javax.websocket.Session;
import javax.websocket.WebSocketContainer;
import org.apache.commons.io.IOUtils;
#ClientEndpoint
public class Client {
private static CountDownLatch latch;
#OnOpen
public void onOpen(Session session) throws IOException {
InputStream inputStream = getClass().getResourceAsStream(
"/myvideo.wmv");
byte[] buffer = new byte[8 * 1024];
while (IOUtils.read(inputStream, buffer) != 0) {
session.getBasicRemote().sendBinary(ByteBuffer.wrap(buffer));
}
}
#OnClose
public void onClose(Session session,CloseReason closeReason) throws IOException {
latch.countDown();
}
#OnMessage
public void processMessage(String message) {
}
#OnError
public void onError(Throwable throwable){
throwable.printStackTrace();
}
public static void main(String[] args) throws DeploymentException,
IOException, InterruptedException {
latch = new CountDownLatch(1);
WebSocketContainer container = ContainerProvider
.getWebSocketContainer();
String uri = "ws://localhost:8081/socket/chat";
Client client = new Client();
container.connectToServer(client, URI.create(uri));
latch.await();
}
}
its works ok but while uploading after a time about 30 seconds an exception is launched :
java.io.ioexception : an existing connection was forcibly closed by the remote host
at sun.nio.ch.SocketDispatcher.read0(Native Method)
at sun.nio.ch.SocketDispatcher.read(SocketDispatcher.java:43)
at sun.nio.ch.IOUtil.readIntoNativeBuffer(IOUtil.java:223)
at sun.nio.ch.IOUtil.read(IOUtil.java:197)
at sun.nio.ch.SocketChannelImpl.read(SocketChannelImpl.java:379)
at org.apache.tomcat.util.net.NioChannel.read(NioChannel.java:140)
at org.apache.coyote.http11.upgrade.NioServletInputStream.fillReadBuffer(NioServletInputStream.java:136)
at org.apache.coyote.http11.upgrade.NioServletInputStream.doRead(NioServletInputStream.java:80)
at org.apache.coyote.http11.upgrade.AbstractServletInputStream.read(AbstractServletInputStream.java:124)
at org.apache.tomcat.websocket.server.WsFrameServer.onDataAvailable(WsFrameServer.java:51)
at org.apache.tomcat.websocket.server.WsHttpUpgradeHandler$WsReadListener.onDataAvailable(WsHttpUpgradeHandler.java:203)
at org.apache.coyote.http11.upgrade.AbstractServletInputStream.onDataAvailable(AbstractServletInputStream.java:198)
at org.apache.coyote.http11.upgrade.AbstractProcessor.upgradeDispatch(AbstractProcessor.java:96)
at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:654)
at org.apache.coyote.http11.Http11NioProtocol$Http11ConnectionHandler.process(Http11NioProtocol.java:223)
at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1558)
at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.run(NioEndpoint.java:1515)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
at java.lang.Thread.run(Thread.java:745)
Someone can help me with this problem ?

JAVA rmi nested exception caused by class not found

I was learning rmi and I came up with a problem and I cannot solve it.
Here is the simple code
client code:
package rmi_test;
import java.rmi.NotBoundException;
import java.rmi.RemoteException;
import java.rmi.registry.LocateRegistry;
import java.rmi.registry.Registry;
public class client {
public static void main(String [] args) throws RemoteException, NotBoundException
{
Registry registry = LocateRegistry.getRegistry("127.0.0.1");
DNInterface s = (DNInterface) registry.lookup("DNInterface");
if (s.test())
System.out.println("Hello World");
}
}
Interface code:
package rmi_test;
import java.rmi.Remote;
import java.rmi.RemoteException;
public interface DNInterface extends Remote{
public boolean test() throws RemoteException;
}
Server Code:
package rmi_test;
import java.rmi.RemoteException;
import java.rmi.registry.LocateRegistry;
import java.rmi.registry.Registry;
import java.rmi.server.UnicastRemoteObject;
public class DataNodeImp implements DNInterface{
#Override
public boolean test() throws RemoteException {
System.out.println("test success");
return true;
}
public DataNodeImp()
{
super();
}
private static void boot() throws RemoteException
{
DNInterface d = new DataNodeImp();
DNInterface stub =
(DNInterface) UnicastRemoteObject.exportObject(d, 0);
Registry registry = LocateRegistry.getRegistry();
registry.rebind("DNInterface", stub);
}
public static void main(String[] args) throws RemoteException
{
String name = "DNInterface";
boot();
}
}
Then I use the following commands to compile the code
javac -cp src: src/rmi_test/DNInterface.java
javac -cp src: src/rmi_test/DataNodeImp.java
javac -cp src: src/rmi_test/client.java
then i type
rmiregistry &
When I try to use
java -cp src: rmi_test.DataNodeImp to run the server
it said
Exception in thread "main" java.rmi.ServerException: RemoteException occurred in server thread; nested exception is:
java.rmi.UnmarshalException: error unmarshalling arguments; nested exception is:
java.lang.ClassNotFoundException: rmi_test.DNInterface
Is there anything wrong with the command I run the code?
Why I cannot find DNInterface.class?
Thank you very much!

The Registry doesn't have that class in its CLASSPATH.
The simplest solution is to use LocateRegistry.createRegistry() in the server JVM rather than rmiregistry.

Getting NotBoundException while writing a Java RMI chat application :-/

I have written a Java RMI chat application. There are four classes and two interfaces. Here they are:
ChatClient
import java.rmi.RemoteException;
import java.rmi.server.UnicastRemoteObject;
import java.util.Scanner;
com.za.tutorial.rmi.server.ChatServerIF;
public class ChatClient extends UnicastRemoteObject implements ChatClientIF,Runnable {
private ChatServerIF chatServer;
private String name = null;
protected ChatClient(String name, ChatServerIF chatServer) throws RemoteException {
this.name = name;
this.chatServer = chatServer;
chatServer.registerChatClient(this);
}
public void retrieveMessage(String message) throws RemoteException {
// TODO Auto-generated method stub
System.out.println(message);
}
public void run() {
Scanner scanner = new Scanner(System.in);
String message;
while(true){
message = scanner.nextLine();
try {
chatServer.broadcastMessage(name + " : " + message);
} catch (RemoteException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
}
ChatClientDriver
import java.net.MalformedURLException;
import java.rmi.Naming;
import java.rmi.NotBoundException;
import java.rmi.RemoteException;
import com.za.tutorial.rmi.server.ChatServerIF;
public class ChatClientDriver {
public static void main(String[] args) throws MalformedURLException, RemoteException, NotBoundException {
String chatServerURL = "rmi://localhost/RMIChatServer";
ChatServerIF chatServer = (ChatServerIF) Naming.lookup(chatServerURL);
new Thread(new ChatClient(args[0],chatServer)).start();
}
}
ChatClientInterface
import java.rmi.Remote;
import java.rmi.RemoteException;
public interface ChatClientIF extends Remote {
void retrieveMessage(String message) throws RemoteException;
}
ChatServer
import java.rmi.RemoteException;
import java.rmi.server.UnicastRemoteObject;
import java.util.ArrayList;
import com.za.tutorial.rmi.client.ChatClientIF;
public class ChatServer extends UnicastRemoteObject implements ChatServerIF {
private ArrayList<ChatClientIF> chatClients;
protected ChatServer() throws RemoteException {
chatClients = new ArrayList<ChatClientIF>();
}
public synchronized void registerChatClient(ChatClientIF chatClient)
throws RemoteException {
this.chatClients.add(chatClient);
}
public synchronized void broadcastMessage(String message) throws RemoteException {
int i = 0;
while(i < chatClients.size()){
chatClients.get(i++).retrieveMessage(message);
}
}
}
ChatServerDriver
import java.net.MalformedURLException;
import java.rmi.Naming;
import java.rmi.RemoteException;
public class ChatServerDriver {
public static void main(String[] args) throws RemoteException, MalformedURLException {
Naming.rebind("RMIChatServer", new ChatServer());
}
}
ChatServerInterface
import java.rmi.Remote;
import java.rmi.RemoteException;
import com.za.tutorial.rmi.client.ChatClientIF;
public interface ChatServerIF extends Remote {
void registerChatClient(ChatClientIF chatClient) throws RemoteException;
void broadcastMessage(String message) throws RemoteException;
}
When I run it on Commando, first of all I run rmic ChatClient and ChatServer, then rmiregistry. Then i run chatServerDriver which works completely fine. after that, when I run chatClientDriver with a name, I get the following error, I dont understand why :/ Can I get any solution for this?
Thanks :)
Exception in thread "main" java.rmi.NotBoundException: RMIChatServer
at sun.rmi.registry.RegistryImpl.lookup(RegistryImpl.java:136)
at sun.rmi.registry.RegistryImpl_Skel.dispatch(Unknown Source)
at sun.rmi.server.UnicastServerRef.oldDispatch(UnicastServerRef.java:409)
at sun.rmi.server.UnicastServerRef.dispatch(UnicastServerRef.java:267)
at sun.rmi.transport.Transport$1.run(Transport.java:177)
at sun.rmi.transport.Transport$1.run(Transport.java:174)
at java.security.AccessController.doPrivileged(Native Method)
at sun.rmi.transport.Transport.serviceCall(Transport.java:173)
at sun.rmi.transport.tcp.TCPTransport.handleMessages(TCPTransport.java:553)
at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.run0(TCPTransport.java:808)
at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.run(TCPTransport.java:667)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1110)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:603)
at java.lang.Thread.run(Thread.java:722)
at sun.rmi.transport.StreamRemoteCall.exceptionReceivedFromServer(Unknown Source)
at sun.rmi.transport.StreamRemoteCall.executeCall(Unknown Source)
at sun.rmi.server.UnicastRef.invoke(Unknown Source)
at sun.rmi.registry.RegistryImpl_Stub.lookup(Unknown Source)
at java.rmi.Naming.lookup(Unknown Source)
at com.za.tutorial.rmi.client.ChatClientDriver.main(ChatClientDriver.java:15)

It also looks like you have a different address in Rebind to what is being used by the client to connect.
Naming.rebind("//localhost/RMIChatServer", new ChatServer());
There's an example implementation on the following Wikipedia page which may be worth comparing against your code.
http://en.wikipedia.org/wiki/Java_remote_method_invocation
Note that using Java 1.5+ you don't need to use rmic anymore see Do we really need to create Stub in java RMI?