We have working on simple definitions and concepts of Distributed Systems in computer networks which are
Replications and Transparency.
so I need to implement RMI client that connects to RMI proxy,then the proxy redirects the client connection to one of n-servers and choose to connect to one of these server based on some value between proxy and server.
so here we have n-servers replications and the client apply the transparency concepts that the client cannot connects directly to servers and from client perspective he can see only one server(proxy server).
Here is simple diagram for what i want to design using RMI only in java...
So, as i have some experience in RMI i implement client and server using RMI
but here Does i need to implement the Proxy server as server to serve the client and as client for the n-servers or what .....????
how to put the first step in implementing proxy using RMI....
Use RMI/IIOP with a load-balancing ORB.
Related
What are the possible ways in which Java Swing Application which is running on client side can communicate with server?
I've read that JSP can be used in web pages to communicate between server and client.But, is it possible to use JSP with Swing application? if so, how? It would be helpful, if it is demonstrated with simple login form. Thanks.
Any client-side application, whether it be a java swing app or otherwise, can certainly communicate with any server (assuming no network limiting architecture -- firewalls and whatnot). Your options are numerous
Raw sockets
Any one of the myriad of network protocols.
HTTP/HTTPS
FTP
SCP
et. al.
It depends on what protocol, services and applications are available on the server to connect with.
HTTP/HTTPS is very common. You'll need to manually create HTTP requests and send them to the server (assuming the server is a web server).
I want to write a program in Netty4 that should act as a server to other clients and also it itself is a client to another server. How to do this in Netty4? So far all examples I have seen are either client or server. Thanks.
There are no special difficulties here. You need to create a part that will act as a server (using ServerBootstrap), and a part that will act as a client (using Bootstrap).
If you need to establish a connection to another server while handling incoming connection from a client, you can place that logic into a ChannelHandler of the server's pipeline.
Netty provides two examples of this approach:
Hex dumping proxy
SOCKS proxy
I'm looking for a secure way to tunnel RMI traffic.
In My application(java Webstart) i must assume that the only port that is open is port 80.
I have the looked att socketfactories for rmi but do i really need a proxy then.
I need to do all my tunneling on the client side.
The only firewall i am trying to get past is on the client side.
I'm not able to open 1099 with port ranges above.
Would be nice to see some implementations.
Thanks!
Port 1099 was reserved for RMI at IANA in about 1995. There is no reason for it not to be open for outbound access in the client-side firewall.
RMI can be made to use fixed port numbers by supplying a port number when constructing (super(port)) or exporting (exportObject(object, port)). Better still, if you create the Registry within the server JVM via LocateRegistry.createRegistry(), all subequently exported remote objects will use that port unless they specify a different port or they use a server socket factory.
BUT ... RMI already includes HTTP tunneling 'out of the box'. No external solution required. You have to deploy the RMI-Servlet provided with the JDK, at the server end.
(a)
although not the newest fashion, exposing remote services with Hessian and Burlap seems to be a simple solution to avoid problem working across firewalls: http://hessian.caucho.com/doc/
see sample code for the server and client side:
http://www.javatpoint.com/spring-remoting-by-hessian-example
(b) or consider using Spring HttpInvokder (see some sample code here: http://www.javatpoint.com/spring-remoting-by-http-invoker-example)
HttpInvokder provides more customization options through the RemoteInvocationFactory, RemoteInvocationExecutor and HttpInvokerRequestExecutor strategies (for example, to add custom context information (such as user credentials) to the remote invocation, or using java’s built-in object serialization etc.), see:
http://docs.spring.io/spring-framework/docs/2.0.x/api/org/springframework/remoting/support/RemoteInvocationFactory.html
I would like to connect to an REST Web Service through a VPN. Is there a way in Java to establish an pptp, l2tp ipsec connection to the VPN gateway an tunnel the HTTP request, without using the Operation System functions? This is important because I will connected to several rest services from a servlet. This Services could be behind different VPNs and I do not want to connect the network of the server with this VPNs.
Do anyone know about an API for that?
If you want to connect to a server behind a private VPN, from the outside, nothing you can do on you app can/will allow you to do connect. Unless you launch a VPN client and programmatically connect your network, to that VPN server, your java app will just sit there waiting for a socket on http connect.
Your question is technically incorrect (not from the SO point of view).
Look for a VPN client library that will pop up a dialog and take username/pwd.
A VPN has the purpose of connecting networks. If you want to reach another system via a VPN you will have to establish a network connection.
a Java API for all of this protocols will be (nearly) impossible, since VPN is handled by OS drivers and not on the application level (where java has its place) in most cases.
If you don't want to have your physical server being connected with those VPNs, you could perhaps set up a virtual system with virtualbox or vmware (or others) which handles all those connections and use it as a proxy. But this is no java issue than.
Here is a simple Java API that allows you to use Nord. I've made several bash scripts that also allow me to start, end and cycle NordIKE-VPN sessions. I have not used this yet, but I am intending on repurposing it for use with Android.
https://github.com/yaniferhaoui/NordVPN-Public-Java-API
I had set up a system that had a Java program running on a server and a Java applet embedded in a page on a client's browser and the two communicating via Java sockets. I'm wondering if I can switch over from a Java applet to just HTML5 and javascript, using a WebSocket on the client side for communication with the Java socket on the server.
Is there a simple way to make a WebSocket communicate with a Java Socket?
Is there a simple way to make a WebSocket communicate with a Java Socket?
From what I understand, WebSocket works by the client side opening a port 80 connect to the server side, and sending a variant HTTP 1.1 request to the server to negotiate a WebSocket connection. If the server recognizes this, it will send a suitable response, and then allow the still open TCP connection to be used for full-duplex client-server interactions.
It looks like it would be possible to quickly put together a server-side that just understood WebSocket negotation and not full HTTP. However, I think you are better off looking at existing WebSocket implementations, including those embedded in HTTP servers / protocol stacks.
This Wikipedia page compares a number of WebSocket implementations, and should help you in deciding which server-side implementation to use.
But to directly answer your literal question, a WebSocket client can only connect to a WebSocket-aware server; i.e. that one that can perform the initial negotiation. (On the client side, you could implement starting from a bare Socket, but you would need to implement all of the "HTTP stuff" on top of that ... for the setup phase.)
Nope, you cannot communicate using regular sockets with client WebSockets.
WebSockets are special HTTP requests, with an upgrade in the HTTP Header, and a standard protocol to establish a connection (see the official RFC doc).