I have a tomcat 7.0.53 server running for the purpose of communicating between java and the website through websockets. I wrote the website script as well as the websocket server java code and they communicate and work correctly. However the information I want passed to the website is from another java program running in the background on a Linux machine. The problem lies however with that when I try to pass messages into a sendmessage type of function on the websocket server java code, it thinks that no sessions are open to send the websocket message to even if I do have the website opening waiting for a message from the separate java process to be passed through the websocket server. I found out this problem arises since I have to make a new instance of the websocket server when passes messages from my separate java process into the websocket server sendmessage function and thus there are no websocket sessions in that instance. I am stumped as to a way around this problem other then to making a socket between my websocket server and the other java process running which will be messy and want to avoid. Does anyone else know anyway else this can be done with communicating a separate java process with a websocket server for tomcat, or is this just impossible to do without making a socket?
I'm not entirely sure I understand your question. Could you share the code you are using to provide more context as to what you are attempting server side?
I believe you should be able to create a websocket client endpoint from the second java program. You can find examples of java websocket clients in the web such as the following:
http://www.hascode.com/2014/11/creating-different-websocket-chat-clients-in-java/
hope this helps
Related
I am trying to write a simple client-server application in Java using HTTP request/response. I would like the client to be a desktop program which sends (posts) a request to a server. The server is a web page which will be hosted on Apache Tomcat server. The server must be able to read the information and display it on the browser and must be able to respond to the client with a status code 200. I am using eclipse and Apache tomcat server. I have so far tried various resources, but all I could find is a client which could request response from an already existing web server. Could someone please give me an example or some insight on how to make the client request the our own server which runs on the local machine.
Good question, though in your case, I won't recommend you implement a simple HTTP request/response approach as you will end up implementing a timer, heartbeat or Comet. You might wanna try javax or jetty WebSocket API. All you need is to create three parts:
a websocket.server
a websocket.client (desktop application)
a javascript websocket client (browser agent)
Your server and both clients will become full-duplex via onMessage and send events.
Here's an example which I believe is a bit relevant one.
https://dzone.com/articles/sample-java-web-socket-client
I am having difficulties understanding the difference between network mode and non-network mode terms as used when dealing with client server applications in java.
I know how to develop simple client server apps. For example I can create a client application and server application. These applications can connect to through sockets and send and receive data. I however get confused when people talk about running a server and client in standalone mode, where both the client and server use the same instance of a JVM without loop back networking involved. I have seen this happening with the java derby database.
So my main question is how do you take code that was using sockets to communicate and convert it to use the so called "standalone mode" where the client and server run as one application? I will appreciate any comments that point me to the right material.
In the so-called network mode you have to connect to a remote server, as you describe, typically through a socket and so your client asks the server to do certain task, the server carries out the task and responds to the client.
In this mode, it is customary that the client and the server will be different nodes, that is different machines, running independently.
But what if you wanted to run you client and your server in the same machine? Even in the same virtual machine? Would it make sense to go through a socket to ask your server to do something?
That would be like using Skype to chat with a friend sat right by your side, to simply ask him to go have lunch.
So, ideally, in these cases, you should be able to run your application in non-network mode. That is, instead of going through a socket, you access your sever object directly and ask it to do something for you. Since your server object is located in the same virtual machine as your client.
Evidently, for you to be able to do this, you need a good design that exposes your server functionality through an interface, and your application uses this interface to interact with the server. When you are running in network mode, you use an implementation of this server interface that uses a socket (or RMI or whatever you do for network communication). When you are in non-network mode, you get an implementation of the server object itself.
i am developing a client/server program in which i want to invoke a method of client program
through server program.
this is vnc based application in which the server will be running and listening to any arbitrary port number .... the client will connect to the server using a method which has argument in the form of ip and port number of server.
after that the server will be able to take control of the client's screen.
i want to call this method from server !!
i want to add a facility in which the client will submit a request and server will then connect to the client ..
i have heard about RMI but i want to know is there any other way available to achieve this if not pls post some good tutorial links on RMI .
RMI is a Java-only way for network programming or method calling but Web Service is language-independent. By web service you can integrate some application.
But my recommendation is using MOM systems. This type of system support two approach : Synchronous Model and 'Asynchronous Model'. In Java MOM is implemented via JMS.(look in here). JMS is an API and have several implementation such as :
Apache ActiveMQ
Open JMS Queue and etc
better than RMI, you could make a web service and a client for it :)
http://www.artima.com/lejava/articles/threeminutes.html
I have a java requirment contains both client and server side program.
Server side
Server program frequently check the data base and checks if a new order came, if order came it check the order and send it to the corresponding client machine using IP address and port.The client machines are out side the LAV and has static IP address.
Client side
Client program listen a its on port , when an order came, read it and process.
For implementing these app, which java package is best,java socket communication or any other.Anybody know please suggest one.
Help is highly appreciated,
Thanks,
vks.
Don't go for low level programming like Sockets etc. Use RMI. Your program will have following two entities
Server side :
An RMI Client for calling client machine to send update after checking the database
Client side :
An RMI server application listening for Server update requests and do processing.
If you are new to RMI check out this tutorial . You can search for better tutorials if don't find these good enough :).
I remember I had to do something similar in the university and I used JMS (Java Messaging Service), documented here:
http://www.oracle.com/technetwork/java/jms/index.html
The Server will create the messages from the DB by checking it periodically and will send messages to the clients which will process the info.
I'm working on a server client base "Desktop Application". And what I want to do is this,
Client application sending some request code to server through internet(oh yes, these connections must be secured). and when server application gets this code it will again do some work and gather some data.
And then server application will return those data again to the client application.
As I am new in this, I need to know, what kind of tools to use?
Is eclipse good for that?
Where can I find good examples for writing client?
Where can I find examples for connecting client with server side?
I'd recomend checking out apache httpclient it really helps when dealing with web APIs.