I want to build system so that :
1. Client connects to Server
2. Client asks for a port to server him
3. Server creates a remote object to serve the Client and binds it to a port
4. return the port number to client
5. Client connects to the port
My session/connection manager
public class ConnectionManager extends UnicastRemoteObject implements Server
{
public List<ClientHandler> clients = Collections.synchronizedList(new ArrayList<>());
public ConnectionManager() throws RemoteException
{
super();
}
public static final String RMI_ID = "Server";
#Override
public boolean checkConnection() throws RemoteException
{
return true;
}
#Override
public int getPort(String ip) throws RemoteException
{
int i = 10000+clients.size()*2;
clients.add(new ClientHandler(ip, i));
return i;
}
}
Session implementation
public class ClientHandler extends UnicastRemoteObject implements Transfer
{
Registry rmi;
Registry reg;
PrintWriter log;
public Client client;
public ClientHandler(String ip, int port) throws RemoteException
{
super();
try
{
File f = new File(ip+" "+new Date()+".txt");
log = new PrintWriter(f);
}catch (Exception e)
{
e.printStackTrace();
}
rmi = LocateRegistry.createRegistry(port);
try
{
rmi.bind(String.valueOf(port),this);
}catch(Exception e)
{
e.printStackTrace();
}
}
The problem that if the object is created in a remote call , it is considered of remote origin and so unless you are on the same host it is not allowed to bind one to the LocalRegistry. and server throws java.rmi.AccessException Registry.Registry.bind disallowed : origin IP address is non-local host.
The problem that if the object is created in a remote call , it is considered of remote origin
Untrue. This is simply not correct. You've just made this up. Don't do that.
and so unless you are on the same host it is not allowed to bind one to the LocalRegistry.
But you are on the same host. The constructor ClientHandler runs in the same host as the ConnectionManager and it creates a Registry, also in the same host. Indeed all this takes place within the same JVM.
and server throws java.rmi.AccessException Registry.Registry.bind disallowed : origin IP address is non-local host.
No it doesn't. I tested your code. After fixing a compilation error it worked. Cannot reproduce.
HOWEVER
You don't need the part about the port, or the extra bind. All remote objects can share the same port. The server only needs to return a new instance of the remote session object to the client, directly.
A simple implementation of your requirement, using your classnames, looks like this, with a certain amount of guesswork as you didn't provide the Server interface:
public interface Server extends Remote
{
boolean checkConnection() throws RemoteException;
Transfer getSession(String ip) throws RemoteException;
}
public class ConnectionManager extends UnicastRemoteObject implements Server
{
public List<ClientHandler> clients = Collections.synchronizedList(new ArrayList<>());
public ConnectionManager() throws RemoteException
{
super();
}
public static final String RMI_ID = "Server";
#Override
public boolean checkConnection() throws RemoteException
{
return true;
}
#Override
public Transfer getSession(String ip) throws RemoteException
{
ClientHandler ch = new ClientHandler(ip);
clients.add(ch);
return ch;
}
}
public class ClientHandler extends UnicastRemoteObject implements Transfer
{
PrintWriter log;
public Client client;
public ClientHandler(String ip) throws RemoteException
{
super();
try
{
File f = new File(ip+" "+new Date()+".txt");
log = new PrintWriter(f);
}
catch (Exception e)
{
e.printStackTrace();
}
}
}
EDIT
It is clear from your post and your comment below that you are suffering from a number of major misconceptions about Java RMI:
if a remote object is created in a remote call , it is not 'considered of remote origin'
The port on which an object is exported has nothing to do with the Registry.
It is determined when you construct an object that extends UnicastRemoteObject, via the super(), call, or when you call UnicastRemoteObject.exportObject() for other objects. If you supply a non-zero port number, that port is used, and can normally shared with other remote objects. Otherwise if there is already an RMI port in use it is shared with this object, otherwise a system-allocated port number is obtained.
Note that the export step precedes the bind step, so it is quite impossible for your misconception to be correct.
You don't need multiple Registries running in the same host. You can use a single one and bind multiple names to it.
If you first call LocateRegistry.createRegistry(), all other remote objects you export from that JVM can share the port with the Registry.
Remote methods can return remote objects.
The Registry is an example: it is actually very little more than a remote hash-map. Your methods can do it too. The objects are replaced by their stubs during the return process.
For those reasons, your intended design is completely fallacious and your comment below complete nonsense.
Further notes:
A do-nothing method doesn't really check a connection. It is just as likely to create a new connection and check that. Connections don't really exist in RMI, or at least they are very well hidden from you, pooled, expired, etc.
You don't need to pass the client's IP address. You can get it at the server from RemoteServer.getClientHost().
The constructor for ClientHandler should not catch IOExceptions internally: it should throw them to the caller, so the caller can be aware of the problem.
Related
I'm using JAVA/Spring MVC and I need to make a Connection Pool for a Third Party Application integration in my application becouse when i try to connect it multiple time my application and server System utilize 100% RAM.
here i have to problem, when users start to hit a specific method (callGenerationService()) multiple time, my Heap memory(RAM space) increases and becomes 100% and application going to slow becouse of it connect third party application multiple times ? here i need to create a connection only once and get it multiple times. where my connection like,
public class ClickToCallServiceImpl implements ClickToCallServiceInterface {
Client client = null;
#Override
public ClickToCall callGenerationService(ClickToCall clickToCall) {
client = new Client();
client.connect("127.0.0.1", 8021 , "password", 10); //Every time Connection Connect.
client.setEventSubscriptions("plain", "all");
// client.sendSyncApiCommand("",""); //here i run command on every hit like.
client.sendSyncApiCommand(clickToCall.command1, clickToCall.command2);
client.close();
}
}
and here 'ClickToCall' is a #Component Bean/POJO Class with variables setters and getters.
Is there, how to we create a connection (either pool or only once connect) for above connection where i connect only once and hit clickToCall.Command1 and clickToCall.Command2 multiple times and utilize less RAM? Thanks in advance.
Please note that I'm not an expert of freeswitch esl so you must check the code properly. Anyway this is what I would do.
First I create a Factory for Client
public class FreeSwitchEslClientFactory extends BasePooledObjectFactory<Client> {
#Override
public Client create() throws Exception {
//Create and connect: NOTE I'M NOT AN EXPERT OF ESL FREESWITCH SO YOU MUST CHECK IT PROPERLY
Client client = new Client();
client.connect("127.0.0.1", 8021 , "password", 10);
client.setEventSubscriptions("plain", "all");
return client;
}
#Override
public PooledObject<Client> wrap(Client obj) {
return new DefaultPooledObject<Client>(obj);
}
}
Then I create a shareable GenericObjectPool:
#Configuration
#ComponentScan(basePackages= {"it.olgna.spring.pool"})
public class CommonPoolConfig {
#Bean("clientPool")
public GenericObjectPool<Client> clientPool(){
GenericObjectPool<Client> result = new GenericObjectPool<Client>(new FreeSwitchEslClientFactory());
//Pool config e.g. max pool dimension
result.setMaxTotal(20);
return result;
}
}
Finally I use the created pool in order to get the Client obj:
#Component
public class FreeSwitchEslCommandSender {
#Autowired
#Qualifier("clientPool")
private GenericObjectPool<Client> pool;
public void sendCommand(String command, String param) throws Exception{
Client client = null;
try {
client = pool.borrowObject();
client.sendSyncApiCommand(command, param);
} finally {
if( client != null ) {
client.close();
}
pool.returnObject(client);
}
}
}
I didn't test (also because I can't) it but it should work. In any case I pray you to properly check the configuration. I don't know if it's OK to always create a Client object and connect or if it's better to connect when you want to send command
I hope it can be useful
EDIT INFORMATION
Sorry I made an error early. You must return the client to the pool
I updated my FreeSwitchEslCommandSender class
Angelo
I'm now processing a client-server communication in Java, by using Socket and ServerSocket objects.
Once the server has been initialised, it puts on hold with new clients through the accept() method, from ServerSocket class; I immediately provide to put this socket in a client map on the server:
- keys: ClientNode(Socket s, CommunicationChannels channels);
- values: Info();
(CommunicationChannels contains ObjectOutputStream and ObjectInputStream from socket; Info contains some information about client, as username, messages etc..).
Given that, at the very beginning, the socket does not have any other information on the client besides the socket itself, first insertion on the map is map.put(ClientNode, null). I will fill the field "value" afterwards.
Now, on Client class, I am going to initialise a Socket("127.0.0.1", 13001), namely with a loopback address and gate 13001. Once communication channels have been initialised, client connects to the server.
Once the client starts, he takes a remote copy of the server through RMI (stub) libraries and the server makes a register() method available: it would allow to use this method to write requested information (from the clients) on the map.
How can the client go back to the socket with which it has been registered on the server? Frankly speaking, I supposed that accept() method from ServerSocket could take the socket established on the startup client back to the server, namely with the new Socket("127.0.0.1", 13001), but it seems to me that this does not happen.
Here you can find parts of the code, so you can better understand what I'm talking about. I've already taken into account a few things that I will share with you in case of need.
public class Server implements Runnable, RemoteServices {
...
private Map<ClientNode, Info> map = new HashMap<ClientNode, Info>();
...
public void run() {
ServerSocket ss = null;
try {
ss = new ServerSocket();
while (true) {
if (!ss.isBound()) {
ss.bind(new InetSocketAddress(ipServer, port));
}
Socket client = ss.accept();
CommunicationChannels channels = new CommunicationChannels(new ObjectOutputStream(client.getOutputStream()), new ObjectInputStream(client.getInputStream()));
map.put(new ClientNode(client, channels), null);
}
} catch (IOException e) {
e.printStackTrace();
}
}
// RemoteServices implementa Remote e mette a disposizione register()
public void register(Info info) throws RemoteException {
// TODO
}
public class Client implements Runnable {
...
...
#Override
public void run() {
Socket client = null;
try {
client = new Socket(ipServer, port);
out = new ObjectOutputStream(client.getOutputStream());
in = new ObjectInputStream(client.getInputStream());
Registry registry = LocateRegistry.getRegistry("127.0.0.1");
stub = (RemoteServices) registry.lookup("remoteObject");
Info info = new Info();
info.setID(getID());
info.setUsername("Giordano");
stub.register(info);
} catch (IOException e) {
System.err.println("Spiacente: il server ha terminato l'esecuzione.");
e.printStackTrace();
} catch (NotBoundException e) {
e.printStackTrace();
}
}
}
Remarks:
I have not included the code of some classes because I thought it was superfluous; for example the "info" class is just a series of "getter and setter" of some fields; the CommunicationChannels class represents communication channels of the client, taken directly from the socket, etc ..
The server, after the accept(), does not instantiate any thread to communicate with the client because communication has to come afterwards. However, if there was a way to solve my problem with a thread of communication I would find a way to fix it.
My question starts from the need to make interact 2 clients with a server without using more PCs; therefore all clients will have the IP loopback and therefore I cannot use the IP address as a discriminating between two sockets, otherwise I would have already solved it.
In other words, I know that methods as socket.getInetAddress().getHostAddress() can help me to distinguish between two socket, but if I initialise two clients on the same PC I have to use loopback address and the method always returns "127.0.0.1".
The register() method is obviously incomplete even in the signature; once understood how to compare the server socket and client one through a Serializable discriminating object (like the hashcode()) probably I might put it in the arguments of the method, so you can easily make the comparison.
Finally, main() methods:
public static void main(String[] args) {
Server server = new Server("127.0.0.1", 13001);
RemoteServices stub;
try {
stub = (RemoteServices) UnicastRemoteObject.exportObject(server, 0);
Registry registry = LocateRegistry.getRegistry();
registry.bind("remoteObject", stub);
(new Thread(server)).start();
} catch (RemoteException e) {
System.err.println("Verificare l'apertura dei registri");
} catch (AlreadyBoundException e) {
System.err.println("Server già attivo. Controllare che i registri siano chiusi correttamente.");
}
}
public static void main(String[] args) { Client client = new Client("127.0.0.1", 13001);
new Thread(client).start();
}
I really hope everything is clear and that you can help me.
While performing a client-server communication with various forums, I am unable to perform Remote-object's lookup on the client machine.
The errors which I receive are ConnectIOException(NoRouteToHostException), and sometimes ConnectException and sometimes someother.
This is not what I want to ask. But, the main concern is how should I setup client platform and server platform --- talking about networking details --- this is what I doubt interferes with my connection.
My questions :-
How should I edit my /etc/hosts file on both client-side and server-side? Server's IP- 192.168.1.8 & Client's IP-192.168.1.100. Means, should I add the system name in both the files:
192.168.1.8 SERVER-1 # on the server side
192.168.1.100 CLIENT-1 # on the client side
Should I edit like this? Can this be one of the possible concerns? I just want to remove any doubts left over to perform the rmi-communication!
Also, I am also setting Server's hostname property using System.setProperty("java.rmi.server.hostname",192.168.1.8); on the server side. Should I do the same on the client-side too?
I've read about setting classpath while running the java program on both server-side as well as the client-side. I did this too,but,again the same exceptions. No difference at all. I've read that since Java update 6u45, classpaths aren't necessary to include! Please throw some light on this too...
If I am missing something, Please enlighten about the same too. A brief idea/link to resources are most preferred.
You don't need any of this unless you have a problem. The most usual problem is the one described in the RMI FAQ #A.1, and editing the hosts file of the server or setting java.rmi.server.hostname in the server JVM is the solution to that.
'No route to host' is a network connectivity problem, not an RMI problem, and not one you'll solve with code or system property settings.
Setting the classpath has nothing to do with network problems.
Here is server example of which transfers an concrete class. This class must be exist in server and client classpath with same structure
Message:
public class MyMessage implements Serializable {
private static final long serialVersionUID = -696658756914311143L;
public String Title;
public String Body;
public MyMessage(String strTitle) {
Title = strTitle;
Body = "";
}
public MyMessage() {
Title = "";
Body = "";
}
}
And here is the server code that gets an message and returns another message:
public class SimpleServer {
public String ServerName;
ServerRemoteObject mRemoteObject;
public SimpleServer(String pServerName) {
ServerName = pServerName;
}
public void bindYourself() {
try {
mRemoteObject = new ServerRemoteObject(this);
java.rmi.registry.Registry iRegistry = LocateRegistry.getRegistry(RegistryContstants.RMIPort);
iRegistry.rebind(RegistryContstants.CMName, mRemoteObject);
} catch (Exception e) {
e.printStackTrace();
mRemoteObject = null;
}
}
public MyMessage handleEvent(MyMessage mMessage) {
MyMessage iMessage = new MyMessage();
iMessage.Body = "Response body";
iMessage.Title = "Response title";
return iMessage;
}
public static void main(String[] server) {
SimpleServer iServer = new SimpleServer("SERVER1");
iServer.bindYourself();
while (true) {
try {
Thread.sleep(10000);
} catch (Exception e) {
e.printStackTrace();
}
}
}
}
and here is the remote interface of server remote object:
public interface ISimpleServer extends java.rmi.Remote{
public MyMessage doaction(MyMessage message) throws java.rmi.RemoteException;
}
all you need is adding MyMessage class both in server and client classpath.
I've implemented an RMI interface with these current files;
MyClient.java - Clientside code
MyServer.java - Serverside code
Adder.java - Interface
AdderRemote.java - Remote _implements Adder_
DataAccess.java - Contains all the methods to interveen between server and client
I have a vps which contains all files except the Client file in the directory
vps:~/rmi#
When testing this on it's own, ie: compiling on the server, doing
rmic AdderRemote
rmiregistry 5000&
(the port I have chosen)
java -classpath .:mysql-connector... MyServer
and then locally doing the same process but running the MyClient java instead, it works. The problem I am facing is now implementing this into a project I have running in eclipse as a part of this;
I have an instance of MyClient in the main file which is then passed as parameters to the certain classes (This project implements the MVC pattern and is passed to fellow model class'), and I am now getting the error
java.rmi.NotBoundException: xox
after googling, the only response I could find was "Attempt to look up a name that is not bound.", But I'm not really sure what this means? I'll attach my code, and any help would be much appreciated.
MyClient.java
public class MyClient
{
public Adder stub;
public MyClient ()
{
try
{
stub = (Adder)Naming.lookup("rmi://92.222.2.96:5000/xox");
}
catch (Exception e)
{
System.out.println(e.toString());
}
}
public static void connect(Adder stub) throws RemoteException
{
System.out.println(stub.connect());
}
Adder.java
public interface Adder extends Remote
{
public String connect() throws RemoteException;
}
AdderRemote.java
public class AdderRemote extends UnicastRemoteObject implements Adder
{
public AdderRemote() throws RemoteException
{
super();
da = new DataAccess();
}
DataAccess da;
public String connect() throws RemoteException
{
return da.connect();
}
DataAccess.java
public class DataAccess
{
// Connection info
static final String URL = "jdbc:mysql://92.222.2.96:3306/groupproj";
static final String DRIVER = "com.mysql.jdbc.Driver";
static final String USERNAME = "root";
static final String PASSWORD = "*****";
Connection c = null;
public String connect()
{
try
{
Class.forName(DRIVER).newInstance(); //Load DB driver
c = DriverManager.getConnection(URL, USERNAME, PASSWORD); //Establish connection to DB2
return "Connected.";
}
catch(Exception e)
{
return e.toString();
}
}
MyServer.java
public class MyServer
{
public static void main ( String args[] )
{
try
{
Adder stub = new AdderRemote();
Naming.rebind("rmi://92.222.2.96:5000/xox", stub);
}
catch ( Exception e )
{
System.out.println(e);
}
}
public static void connect(Adder stub) throws RemoteException
{
try
{
stub.connect();
}
catch(Exception e)
{
System.out.println("Could not connect to the DB.");
}
}
I gathered that because the files on the server are located in the directory "rmi" I renamed the xox to this, but this did not solve the problem, so I reverted it back to xox, which it worked before putting it into a java project.
Thank you
You must have got an exception doing the bind.
If you got a NotBoundException when looking up the same name in the same Registry you're supposed to have bound it to, you didn't bind it at all.
Notes:
You can only bind to a Registry that is running in the same host as yourself. For that reason it is convenient to always use "localhost" as the hostname when calling bind(), rebind(), or unbind().
You'd be better off letting the RemoteException and NotBoundException be thrown from the constructor of MyClient.
MyClient.connect() should not be static. In fact it cannot be static. Ergo this cannot be the real code.
From what we can see so far, your system isn't correctly designed. Your server should get a DBMS connection when it needs one, inside a remote method, on behalf of the client that is calling that method, and release it before exiting the method. Opening a new connection every time a client asks for one explicity and storing it into an instance variable of the remote object (a) will leak connections and (b) won't work when concurrent clients come to execute a query or update on the same connection.
I'm using RMI, I have an string obj in my server (or a client) and i want to send it to all clients, how can i do this?
public class Myclass extends UnicastRemoteObject implements Server {
Connection c=(Connection)DriverManager.getConnection("jdbc:mysql://localhost:3306","root","123");
String str2="";
Myclass()throws Exception{
LocateRegistry.createRegistry(1099);
Naming.rebind("My Class!!",this);
Class.forName("com.mysql.jdbc.Driver");
}
//the override is cause of the interface 'Server'
#Override
public String Reciever(String str1) throws Exception {
str2="Say Hello to "+str1;
return str2;
}
public static void main(String[] args) throws Exception {
Myclass mc=new Myclass();
}
}
in this class str2 will send to that client which is running Reciever(), how to send it to all clients?
RMI servers don't send to clients. They respond to clients, when they send a request, by calling a remote method. The server response is sent as the return value. You will have to have the clients poll the server for these messages, or else make your clients into servers as well.
From the client code, find the service and then request the server object and you can then call remote methods on this class.
http://docs.oracle.com/javase/tutorial/rmi/client.html
Also why is Reciever() capitalised? It's standard practice for methods to be in camel case (lower case start, upper case for first letter of new words).
Not sure if your server is correct either, you should take a look at this tutorial to ensure you understand how and why RMI works. It's not a long tutorial. http://docs.oracle.com/javase/tutorial/rmi/overview.html