Real time Java Communication

I need help on developing a elearning application that enables real time communication. Can anyone help me on how to start to who can help me?

Hi,
I pretty new in Java. My understanding of both of the applications is very vague. Can you help me over here? Are those yahoo games considered stand alone?
Currently i have developed a GUI, bascically an interface for users to communicate. However, that is only a dummy without any event driven. I was wondering what is needed to allow users to communicate real time. For eg...chat function like icq or audio coomunication like video conferencing. Thanks! Pls advise.

Similar Messages

Scheduling in Real-Time Java

Hello,
I have some questions concerning how scheduling in fact is intended to be performed in a RTSJ based Real-Time Java System.
As far as I understood, RTSJ requires pre-emptive priority-based dispatching of Schedulable objects.
This means that the execution eligibility of a schedulable entity is mainly its priority.
That causality is reflected within the specification with the (one-and-only specified) PriorityScheduler, which is the base scheduler for actual Real-Time Java applications.
Furthermore, there is a notion of extensibility of that PriorityScheduler described by RTSJ,
in order to provide further scheduling mechanims and feasibility analysis algorithms (please correct me if there are any wrong assumptions).
This is the point, where everything becomes really weird to me ...
As far as I could investigate, in most RTSJ implementations based on a POSIX compliant system underneath (like Java RTS does on RTLinux or Solaris)
each (Realtime)JavaThread is mapped 1-to-1 to a light-weight process on the operating system level (e.g. a pthread).
So far, we have no "green threads" within the JVM, but real LWPs scheduled by the OS.
The difference between "normal" and "real-time" threads lies in the scheduling policy used for that mapping.
While normal Java threads probably map to SCHED_RR or SCHED_OTHER, real-time threads are scheduled by the OS via the SCHED_FIFO policy in order to achieve a better real-time predictability.
However, the OS's scheduling mechanisms automatically make decisions about the right positioning of a LWP within an appropriate run-queue, due to thread's preemption, blocking or release (even dynamic priority changes) activities and its scheduling policy.
That's exactly why I ask myself, what is the need of a Scheduler representation within a JVM?
Furthermore, how a Scheduler extension is able to incorporate with the threading model and the underlying scheduling mechanisms of the OS?
One point could be a situation where a real-time JVM runs directly on top of the bare hardware and has to perform scheduling decisions on its own.
The Scheduler API could then be understood as an extension mechanism of a kind of JVM-intern scheduler (e.g. the PriorityScheduler), thereby allowing scheduling decisions to be made even in user defined Scheduler implementations.
A similar use case for an OS-based scenario could be if a JVM is intended to pass scheduling/threading routines of the underlying OS (eg. a part of the POSIX API)
up to the Java application level in order to provide the opportunity for a kind of application defined scheduling (like e.g. in the MaRTE OS).
Unfortunatelly, after introspecting the RTSJ API, both conclusions seem to me to be wrong.
So far, Java RTS seems not to provide any mechanism for reaction on scheduling events/decisions, neither intra-JVM nor from an underlying OS outside of the JVM.
Furthermore, there is no notion for incorporation with the base PriorityScheduler for making extended scheduling decisions.
I hope this post could bring me more light into the scheduling idea behind Real-Time Java systems as intnded by the RTSJ.
Sincerely,
Vladimir

Vladimir.Nikolov wrote:
That means, that a scheduling policy different to PriorityScheduler can only be assigned to a Schedulable object if it is supported by the OS and the JVM?Well it has to be supported by that implementation of the RTSJ. Howe that is done - ie whether it requires OS support - depends on that VM, the OS and the actual scheduling policy.
It also seems that at the current state of the art the PriorityScheduler representative within the JVM is intended only for manipulating a feasibility set of Schedulable objects (supporting online feasibility analysis)?
However, since user-defined scheduling is not intended by the specification, applications have to rely on the feasibility analysis based on the underlying/supported scheduling mechanisms.
Thus, in the current Java RTS implementation this would be the "default" feasibility mechanism based on the PriorityScheduler.
Unfortunatelly I can not figure out the need of maintaining a feasibility set, since feasibility, as specified for the PriorityScheduler, is a simple asumption that we have "an adequatly fast machine to handle the periodic and sporadic load"?
I actually assumed that feasibility analysis performs real cost budgeting taking into account deadlines and so on, but it seems to be specified simply to make a negative statement always when aperiodic tasks are involved ?The RTSJ scheduling framework provides support for feasibility analysis by defining the admission control methods eg setXXXIfFeasible. However the RTSJ does not, and can not, mandate any non-trivial feasibility algorithm because in simple terms no such general algorithms exist. There are some static feasibility tests in the literature and you could apply those offline to your application (assuming you can find the values of all the "magic" numbers in such formulae - which is generally not the case). At present the RTSJ doesn't support even these simple feasibility tests because blocking-time is not recorded in the release parameters - something being addressed in RTSJ 1.1. In any case unless there is a pluggable framework for feasibility tests it would be a waste of time for VMs to implement them given they can (more) easily be done offline using other tools.
Only dynamic admission control is really of interest and as far as I am aware no such general dynamic admission control policies exist (anything you find in the literature is very context specific). So it is left up to an implementation as to whether they try and define dynamic admission control algorithms - and so far none have because they don't have one.
In "Getting More Flexible Scheduling in the RTSJ" Wellings and Zerzelidis propose some (more or less) "minor" extensions to the RTSJ API in order to enable hierarchical scheduling within the fixed priority framework.
Since Andy Wellings is a member of the RTSJ Technical Interpretation Committee, is there any attempt to evolve the specification in a similar direction as described above, in order to support more flexible scheduling mechanisms and feasibility analysis?If there is ever a RTSJ 2.0 then more sophisticated scheduling support is one of the items on the wishlist. But there's no guarantee there ever will be a RTSJ 2.0
David Holmes

Regarding real time java packages

Hi,
I am relatively new to java. can anybody tell me about real time java, and where can i find the implementation of javax.realtime package?

i have found a real time java specification which has a package javax.realtime which lists some classes like timer,asyncevent etc. that would be helpful for me. i am supposed to use j9 jvm on qnx rtos. but these classes dont come with standard jdk. can u tell me how to proceed?

AspectJ with real time java

Hi
Does real time java supports aspectJ with Load-time weaving ( LTW ) ? ( compile time weaving )

Not sure what you mean by "support". AspectJ rewrites bytecodes so the VM will just execute them. You'll probably encounter increased memory usage with load-time weaving as class loading/initialization occurs in Immortal memory. Also load-time weaving won't be compatible with Java RTS's Initialization Time Compilation (ITC) feature ... or at least not the pre-initialization part. It's likely that no-heap threads won't work well running weaved code if there are any references back to heap-allocated AspectJ runtime objects, and similarly (like most libraries) it's not likely to work from scoped memory.
HTH.
David Holmes

Real Time Java

Hi. I am required to design a Real Time project using Real Time Java. The problem is that I have no idea what I can do in the time allocated (two weeks).
Anybody have any idea what could be interesting to do, or have pointers where to look?
Thanks
Eric
P.S Sorry if there's a Real Time Forum.

Ouch.
In a real time system, you absolutely positively must have certain events happen at specific moments in time, regardless of what else the CPU might be doing.
To use a poorly timed example, a rocket booster on the space shuttle must ignite its engine exactly five minutes, three seconds after take off - even if the computer is busy processing the latest SETI data. In other words, time based pre-emptive multitasking.
The closest you can come to it is using threads to start and suspend tasks according to the system clock. So for something codeable in two weeks...
Look on the web for two suitable compute-intensive mathematical algorthims. RSA key generation would be one.
Put each algorithm into its own thread. Add a third thread that explictly saves the current system time to a file every five minutes. So I would see something like...
Thursday April 03 2003 13:22:05
Thursday April 03 2003 13:27:23
Thursday April 03 2003 13:32:18
As the output. Notice the variation in seconds. If you did it right and it works in real time, there should be no variation - it saves at 05 seconds on the dot each and every time.
If you want more suggestions or advice, I suggest asking over on the "advanced language topics" or "algorithms" boards. Do NOT cross-post!

Real-time support in Java SE Embedded

From what I understand, Java SE Embedded is a slimmed down SE JDK/JRE compiled to support different typical embedded processors, ARM etc.
Does Java SE Embedded provide any additional support for handling realtime situations? For example, are there any JVM modifications to guarantee response times and execution times for time critical scenarios?
The reason for asking is that I know a while back there was a specific Real Time Java release - did any of this technology get rolled into the new SE Embedded?
Thanks.

Yes, Java3D or an openGL toolkit such as JOGL or LWJGL is probably the best choice. Bearing in mind that Java3D is on the way out you may want to look at using OpenGL although there is much talk over at javagaming.org of putting together an open-source Java3D-like scenegraph renderer for the openGL toolkits and the guy working on it is very good indeed so it will probably happen. Assuming that it does, time spent learning Java3D is not wasted time.
If you are interested in Java3D download the API and tutorials and see how you get on with it. I put together a fairly gaming oriented tutorial here http://www.newview.co.uk/e/tutorials/java3d/index.jsp which may help you get started.
If you are serious about writing games in Java you will want to get over to the javagaming forums http://www.javagaming.org/cgi-bin/JGNetForums/YaBB.cgi because that is where you can generally find the best advice. There are a number of old threads on this question there and you will probably find it well worth your while to look through the older posts on it.

Need urgent help in Real Time scheduling algorithm implementation

I am new to Java Real Time programming. I have faced a problem which is stated below:
Declare tasks
for
if it is schedulable then run the task
otherwise it is not schedulable
for
check priority with respect to deadline.
select highest priority task
for
start higest priority task
if the task is preemtable
then switch lowest priority task to highest priority task and stop the lowest priority task
after completion higest priority task, lowest priority task complete the rest of the work.
this is actually a pseudocode for real time dynamic scheduling ( rate monotonic scheduling). can anyone please help me develop the code?

PrinceOfLight wrote:
I am new to Java Real Time programming.
this is actually a pseudocode for real time dynamic scheduling Define "real-time" in your context. Most people who use the term don't use it correctly. If you truly mean "real-time," then you'll need real-time Java running on a real-time OS.
can anyone please help me develop the code?What specific problems are you having? If you have no clue where to start, this site is not a good resource.

Real time OS?

Is the kernel of solaris 10 a real time kernel? I mean on solaris 10 can I code and run application developed in real time java?

Should work, at least if you have two CPU's, then you can use one of the CPU's to recieve hardware interrupts, sync filesystems etc and the other one can be used to run your rt application.
//M:

Real Time Kernel patch

Hi,
Has anyone tried to add the realtime kernel patch to an existing arch installation?
Can anyone provide home help ?
I want to add the RT patch so i can use some Real Time Java implementations on arch

As you can see, a bit of googling would have solved your problems. Now, please go read the wiki on custom kernels and the AUR before asking questions about how to use those.

Labview Real-Time and CompactRIO questions

Hi
everyone! We have new troubles about CompactRio and Real Time module:
-We want to
translate into real-time module a VI we have done with Labview 8 .2. In order
to do that we have discovered an option placed in Project Explorer (Tools->Real-Time
module->Communication Wizard) that seems to translate automatically into Real-Time
language. Is it true?
- If it was
true we would want to do a transmitter VI in CompactRio (RT target) and a receiver VI in the Host. But the
Communication Wizard creates a VI in the Host and a VI in the RT target (in
Real Time language) for each VI we enter to translate ( so we obtain 4 VI’s in
the same project , two of them as transmitter, and two of them as receiver)
-We have
tried to deploy some VI’s to the CompactRio and we get always an error.
CompactRio’s configuration is allright and it is well recognized by MAX. Why
does the error appear, and how can we work it out?
We
need to configure the Serial Port placed in CompactRio in order to adjust some
features, such us bauds value. MAX recognized the CompactRio’s Serial Port, but
all the opctions to configure them are disabled.
I hope you
can answer these questions. Thank you.
Ander

Hi again,
Still didn't find the problem on my side. Here's a picture of my code. If I put the code surrended in red at place (1), I don't get the error, but if I put the code at place (2), I get the error. Why oh why....?
I get the error when I close the browser or click Back button of the browser or Stop the application with the red dot or stop the application with the Quit button on my front panel.
This morning I found a post on this forum about getting an error using Property node and Remote panel (http://forums.ni.com/ni/board/message?board.id=170&message.id=252705). I did what they suggest: wire the property output to an indicator and it works (disable "Enable automatic error handling dialod" didn't work... I don't know why)... until I put extra code in my VI.
I really need help please!
Thank you
Stephanie
Attachments:
MemoryManager line 437 error.JPG ‏228 KB

Using wireless network with Real-Time system

Hi,
Has anyone tried to run a LabVIEW real time system communicating over a wireless network instead of wired Ethernet? Thanks.

I would think that all you need to do is hook it up to a wireless access point and the system - whatever it is - wouldn't even know it was hooked up wirelessly...
Bill
(Mid-Level minion.)
My support system ensures that I don't look totally incompetent.
Proud to say that I've progressed beyond knowing just enough to be dangerous. I now know enough to know that I have no clue about anything at all.

CVI RT (Real Time) - HOST TCP/IP Communication

Hi,
I am using CVI 2012 Real Time with PXI hardware. I am using TCP/IP communication b/n RT and Host. RT is server and Host is client. In my application, after TCP connection is established between client and server, client will send a command , take for example "GET_DATA" to RT, RT has to respond to that by sending that data.
I am successful in
Establishing RT-Host TCP communication ( I am able to see that host is reading the welcome message sent by RT).
Host is sending the command "GET_DATA" to RT.
RT is receiving the "GET_DATA" command from Host.
In TCP server call back function, in TCP_DATAREADY event, i am using ServerTCPRead() to read data from Host. After reading the data, i am comparing the data with expected command and based on that i will be sending the data using ServerTCPWrite().
RT is reading the command from Host, but it is not writing the data to client. I am not sure whether I can use ServerTCPWrite() in TCP Server call back function.
I also tried using multithreaded concept, but not getting success.
Please suggest any solution for this.
Thanks,
Haari

Hey Rashid,
Check out this tutorial with examples and let me know if it helps.
Stephanie O.
DIAdem Product Manager
National Instruments

Real Time TCP/IP communication

Hi,
I am using the following hardware:
PXIe-1062Q
PXIe-8108
PXI-5600 (02 card for 40MHz Bandwidth)
PXIe-5641R (both inputs are used; one for each PXI-5600)
PMA-1115
Labview 2009
I am using instrument mode to detect the real time hopping signal and writing it to a spreadsheet.
My question is that how can I transfer data on LAN in real time to create a waveform in software on a remote computer before writing it to spreadsheet. I am looking for something like real time TCP/IP communication.I have attached my VI. Kindly guide me that how can I do this?
Thanks and Regards,
Rashid
Solved!
Go to Solution.
Attachments:
FOR.vi ‏54 KB

Hey Rashid,
Check out this tutorial with examples and let me know if it helps.
Stephanie O.
DIAdem Product Manager
National Instruments

Jmx with java real time

Hi David,
my question for now is very general.
can we use jmx with jrts???
Gabi

Hi Gabi,
Some additional information:
- JavaRTS does support the JMX protocol
- JavaRTS supports most of the monitoring & management functionalities provided
by HotSpot MBeans
- some functionalities are disabled by default because they would create jitter (like
getting the stack trace of java threads). Default can be changed through the
realtime.debug MBean)
- JavaRTS comes with a few additional realtime specific monitoring beans.
Note that JMX relies on threads to do its work. These threads are not real-time.
Hence, if the realtime threads (including the RTGC) are consumming all the CPU,
you may not be able to call MBeans to see what is happening and take corrective actions.
Bertrand.

Real Time Communication

HI Gurus,
Can any one tell me what is REAL TIME COMMUNICATION.
Also I request information / details on RTCIS.
Regards
Ajoy

Hi Ajoy,
1.1 Application Scenarios for Real Time Communications
There are two classes of applications: client and server. Client class applications have one real-time client per computer, such as the traditional instant messenger (IM) application. Server class applications typically act on behalf of multiple users or communicate with many hundreds of users simultaneously. Server class applications are often based around intelligent applications that interact with users. These applications can be divided into two categories: notification Apps that send information to a client and interactive Apps that accept and respond to a client. A third type of server class applications, Web-based clients, interacts with users through a Web server.
1.2 Notification Applications
Notification Apps are real-time applications that send information to multiple clients from a centralized server (see Figure 1). The one-way transmission means that clients cannot communicate directly with the notification App. Instead, clients must choose which events they wish to receive by using some other technique, such as a Web application.
One example of a notification App is an application that notifies all of the users of a particular e-mail server that the server is about to go offline. Another useful notification App would send alerts in cases of severe weather.
1.3 Interactive Apps
Interactive Apps are applications that allow multiple clients to communicate with a central server in real-time, as Figure 2 shows. They are different from notification bots in that interactive bots support two-way communications with a client. Using this approach, you can build an application that interacts with users in real-time. Within this scenario, there are two main sub-scenarios. The first provides a user with information and waits for the user to respond, such as an application that notifies users about changes in stock prices and then gives the user the option to buy or sell. The second waits for the user to request a session with the App and then responds to requests that the user supplies, such as a calendar application that allows a user to schedule meetings and other events while receiving reminders just prior to the meeting or event.
1.4 Web-Based Clients
Web-based clients provide the same basic functionality as the traditional IM client through a Web interface, thus allowing the widest possible audience to use the application, as Figure 3 illustrates. It also has the side effect of eliminating the need for a user to download local software, which reduces user concerns about the download containing a potential virus. These types of clients are useful to organizations that wish to provide a Web-based front end to their internal IM system. For example, a company might wish to use a Web-based IM client to connect customers with a support group. Doing so maximizes the number of customers that can connect with the support group.
Real Time Communications Data Flow
It's critical that organizations planning large deployments of real-time communications applications ensure that those applications can scale to meet the desired goals. The RTC Client API is very efficient for client class applications for which each client runs on its own computer. To build a scalable RTC Client API application that services multiple clients with a single computer, you need to ensure that the application is scalable when you design it.
The Real-time Communications (RTC) Client API is a set of COM interfaces and methods designed to create PC-PC, PC-phone, phone-phone audio/video calls, or text-only Instant Messaging (IM) sessions over the Internet. Application sharing and whiteboard (An application that displays a window for two users to exchange information) can also be added to PC-PC sessions. Presence information is used to track the location of buddies (or contacts) for communication purposes. This information is available through the RTC Client API on a SIP registrar server.
The RTC Client API:
1.Supports multiparty phone-phone calls
2.Uses SIP-based signaling and presence communications
3.Integrates with the Microsoft Office RTC proxy and registrar server
4.Supports provisioning with ITSPs or third-party corporate-deployed servers
5.Integrates signals over IP and PSTN networks
I hope this will be useful for you.
Thanks,
Swamy Kunche

Real time Java Communication

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