I'm trying to write a multiplayer realtime game and run it on CloudBees (the client side is an applet, the server side a java web application). Is it possible to give the server permission to listen on another port? (ie so the server-side code can create a ServerSocket on that port and the client side code can create a Socket to connect and communicate with the server)
Whilst it may be possible it is quite tricky as the available port is likely to change as your app moves around. On top of this - you would need to locate the address of the instance of where your app is running (ie some kind of dynamic directory) - so kind of fiddly. The web routing layer does all this for you - but presumes http or similar (you can use "long poll" and keep a connection open from an applet - this could work in a similar way, with some work).
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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 have created one sample chat application. In that chat application, I used JApplet and front end.
Till now I was testing my application in my desktop. It is working fine. Now I want to deploy my application over any webserver.
Now I have a few questions. Currently I am using Server socket as 8989 in my chatserver. When I was testing the application in my desktop, I used to start the server as stand alone.
What are the steps I have to follow when I deploy the application over tomcat or any other web server? Which port the client will listen?
How do I start my chat server? I am new to the socket concepts.
when you say you are hosting on the webserver, i believe that its an servlet/jsp based application , which will listen to your requests , in that case the listener will be invoked at the webserver default port either 80 / 8080 (being default). In case you want to change or check , you can go to the TOMCAT_INSTALLATION_DIR/conf/server.xml and check for tag containing the port number for weblistener, and change it to whatever value you feel like.
if thats not the case and you have your own thread which opens a socket for you , you really dont need a webserver, all you need is a host machine which will start the socket listener ( your custom) and then it will listen at the port that you have configured it to be at.
As far as I got it, you're having standalone application as a server, where you handle connections to particular port.
I think there is some confusion that should be clarified.
The very basic question is:
Why do you need your chat server to be running on the web server?
This should be clear to you prio to any later steps.
As web server is there basically to handle HTTP/S requests and that's not your case, as far as I got it. As you're probably running socket TCP/UDP communication.
For the web server however your client applet implemnentation could benefit of. If it would be referrend on a simple html page (deployed inside war) it could be simply redistributable to clients via url call in a web browser.
Maybe I'd preffer to use HTTP + JSON commununication, where you could benefit from web server usage (also on the server side) and would not need any other ports than standard ones.
Not sure if it still makes sence to answer your questions as it might be irrelevant for you, but let's see.
Answers to your questions:
Basically you need war archive (rather than jar one), as that's the one accepted by web servers. once you create it (you need to follow the correct folder/file structure inside) your app could be deployed to web server.
Which port the client will listen? Basically server is the listener here => no client port listening here.
This depends on your communication implementation decision. If still sticking with TCP/UDP one, I don't think web server would be beneficial here.
Is it possible to write a Java applet that can be a server on the client machine within the client's local network?
To be more specific, what I am looking to do is tunnel non-web traffic over the web. The sender would send to the applet, which would then forward the received data back to the server.
Is this sort of thing possible? What are the restrictions that might get in the way?
Note: I know that the applet can connect back to the server, that isn't an issue. The issue is whether or not an applet can listen for a connection / data on a local, client-side port.
An unsigned applet can only connect the host they come from.
A signed applet can do any connection you want and can listen on tcp-ip ports.
Source : http://docs.oracle.com/javase/tutorial/deployment/applet/security.html
Server does not connect to anywhere. Server opens server socket and is listening.
In past as far as I remember the server socket was restricted in MSIE and was permitted in Netscape (do you remember such browser?) :)
I personally have not been writing applets for the last 10 years, so I have no idea what happens now with currently existing browsers, but it is very easy to check. Just write the shortest applet you can and put code new ServerSocket(1234).accept(); into its init() or start() method. If no exception was thrown you can write applet that functions as a server. Otherwise you cannot.
Just try it with all available browsers. 20 minutes work and you are done. Good luck. I'd will be glad to know about the results.
Generally, it cannot.
One reason why is that applets tend to be ran within security constrained environments, which means that they are denied the ability to open server sockets.
There are ways around such a restriction, basically you can specify a special security policy for the applet, or run it in a special unconstrained container; but why bother when you can just port the contents of your application into a standard servlet, or even a stand-alone server?
which is the best method to send a numerical value data from a javscript webpage to a web server port.. i have a server socket program running on the server and listening to port 5000.
i need to send data from a webpage to the port? which is the best method?
the scene is this.
i have a C socket program running at a web server hosted in my laptop using XAMPP.
it is listeing to a port 5000 and also i have my ip address. in the web page,
i am running a javascript and when the user presses any of the arrow keys i need a value to be sent to this port.. like up -1 , down -2 etc ...
There isn't currently any way to do this in a portable fashion. Some browsers support the WebSocket standard, which gives you some limited access to sockets, but this isn't currently available in any common browsers other than Chrome and Safari. The Flash player supports a separate XMLSocket protocol, which you can also use if the Flash plugin is available. However, neither of these protocols supports raw access to sockets -- both require some initial negotiation and packet framing.
Because your web server is running on a different port than your socket program, the Javascript in the browser is restricted from making requests directly to the socket program because of the Same Origin Policy. However, there are various ways to get around this restriction. Alex Sexton has a lengthy overview of all the different ways of doing this. However, all of those ways require that your socket program be running the http protocol also.
Socket.IO seems like a perfect fit for what you are trying to do, but you'll probably need to ditch your C program.
The only way to open a network socket connection from a web page is to use a Java or Flash app to make the binary socket connection. You could then use java script to pass the data to the app which would connect and forward it to the server.
Alternatively you could use some server side code and AJAX to proxy the connection and forward the data.
The second option doesn’t rely on any browser plug-in being installed and I think would be easier to implement. It would also be able to forward to a port that is not on the web server itself as it wouldn’t be subject to browser security restrictions.
I guess making one ajax request to required port on a server... can solve the request.
I created a game and I want to put it on online. I want to buy a website (I'll probably use goddaddy to buy a domain name and use them as the web host) to use as the server to handle game play. Because I would need a separate server for each game, I would need each game's server to exists on different ports. So this leads to my question, is is possible to access these ports on my future web server? (I wrote the program in Java, so I would assume that I would access the ports from the server side by choosing a port for a ServerSocket, and from the client side by using the IP address from the website and the chosen port for a Socket)
(note: also, I am aware that it may be easier to simply use one port and run the servers on different threads instead, but I am just curious to have my question answered)
thanks a lot,
Ian
Technically it is possible to use different ports, but I don't think that a webhoster like goddaddy will let you run a java process that binds to a special port.
If you mean that you are going to create your own TCP server you obviously can create as many instances of your server and configure them to listen to different ports. But it is year 2011 now. This solution was OK in early 90s.
I'd suggest you to use Restful API that works over HTTP. In this case you can forward calls to server side of each application using URL, e.g.
http://www.lan.com/foo/login?user=u123&password=123456 - log in into application foo
http://www.lan.com/bar/login?user=u123&password=123456 - log in into application bar
In this case you need only one server (the web server) that is listening to socket (port 80).
Your server side implementation could be done using various web techonlogis (php, java, asp.net etc) on your choice.
Yes, that should work. The security manager permits connections to a different port on the same IP address that the applet was loaded from.
You can run a Java server on whatever port you want. Each server will accept incoming requests on one port.
The correct way is simply run on one port and each connection will instantiate a new servlet instance (which happens to run in its own thread) that can then service that request. You usually don't need to run separate ports or worry about concurrency, especially if all the stuff that's shared between connections (e.g. multiple players in one game) is handled through database read/writes.
Your host (GoDaddy) will have to allow you use of those ports, but if they are providing proper hosting (not virtual hosting) and given you your own IP there's no reason why you shouldn't be able to.
Your solution may work theoritically, and I like AlexR's solution. But providers like godaddy doesnt let you run a java server, on ANY port. You will need to find out somebody who does. What I found is the cost goes up from $5/mo to about $20/mo, but you get a much better (read faster) machine. Good wishes, - MS.