Client/Server how to synchronize methods execution on clients

Question

4.00/5 (1 vote)

See more:

I need a simple client server application that allows the server to send a command to all clients that will run a method at the same time.
How can I make sure that the clients will perform the method at the same time?(milliseconds of delay)
I thought the use of SNTP but I do not know how to integrate it.
Any suggestions?

[Edit]
I need to start a video at exactly the same time on a LAN enviroment.
The video is on client machines (No broadcast).
The playback between client machines must be synchronized
Should support up to 50 clients.
The server machine will be near (50 meters)
[/Edit]

Sorry for bad english

Posted 4-Jun-11 5:43am

Morph King

Updated 4-Jun-11 7:26am

v7

Add a Solution

2 solutions

Add a Solution

Add your solution here

Treat my content as plain text, not as HTML

Preview 0

…

Existing Members

Sign in to your account

...or Join us

Download, Vote, Comment, Publish.

Your Email
Password
Forgot your password?

Your Email
This email is in use. Do you need your password?
Optional Password

I have read and agree to the Terms of Service and Privacy Policy
Please subscribe me to the CodeProject newsletters

When answering a question please:

Read the question carefully.
Understand that English isn't everyone's first language so be lenient of bad spelling and grammar.
If a question is poorly phrased then either ask for clarification, ignore it, or edit the question and fix the problem. Insults are not welcome.
Don't tell someone to read the manual. Chances are they have and don't get it. Provide an answer or move on to the next question.

Let's work to help developers, not make them feel stupid.

This content, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

Manfred Rudolf Bihy · Answer 1 · 2011-06-04T06:44:00

Solution 1

Synchronize your computers via NTP (> Windows 2000) or SNTP (<= Windows 2000) using the Windows Time Service[^]. The server could add scheduled jobs on all clients to start at a specified time and run once as they'll be rescheduled by the server when appropriate.

Beware though: "However, the Windows Time Service cannot maintain the system time more accurately than about a 1-2 second range" (Wiki Reference[^]).

So if "at the same time" means that a difference of 1-2 seconds is OK by your requirements, this might be a viable solution. For a great tool to setup, run, delete tasks on remote machines use CodeProjects own TaskScheduler Library[^] written by Dennis Austin[^]. David Hall's[^] TaskScheduler Library on CodePlex[^] is also worth a look.

I hope this will help you. It should be no problem as long as the accuracy of Windows Time Service synchroization is good enough for your application.

Best Regards and happy coding,

-MRB

Posted 4-Jun-11 6:44am

Manfred Rudolf Bihy

Updated 4-Jun-11 6:53am

v4

Comments

Morph King 4-Jun-11 12:52pm

I need to start a video at exactly the same time, we are talking about milliseconds of delay

Manfred Rudolf Bihy 4-Jun-11 12:56pm

What kind application is that? A video should be broadcast by a streaming server and the clients would receive it if the proper application was previously started before the broadcast.
You will have to lay out your exact requirements to get real good help.

Manfred Rudolf Bihy 4-Jun-11 13:01pm

Milliseconds are not realistic in a network environment. Especially when in a WAN environment you'd have to cope with latencies too.

Morph King 4-Jun-11 13:01pm

The video is already on the client machines, when the server sends the command the clients must start the playback at exactly the same time.
it's a LAN Network.

Manfred Rudolf Bihy 4-Jun-11 13:03pm

You still have not come up with a plausible reason for why this would have to be at the exact same time. Please explain.

Morph King 4-Jun-11 13:07pm

because every client will playback a portion of the video, monitors will be alligned

Manfred Rudolf Bihy 4-Jun-11 13:11pm

Thanks Morph, I was thinking already in that direction. Please edit your question with "Improve question" and add these valuable details. Also mark the edited section with [Edit] [/Edit] so people will know that the information was added.

Please also note how many clients will be in this scenario and if the the server you were talking about is also in the vicinity.

Morph King 4-Jun-11 13:23pm

I've edited the question, now that you understood what i'm talking about did you have some suggestions?

Manfred Rudolf Bihy · Answer 2 · 2011-06-04T08:13:00

I've added this as a separate solution since the requirements where not known from the start.

I presume the machines are dedicated to this task only and don't have any other purpose than to play one video spread over several screens
Have the application run when the machines are started.
The machines send some sort of ready signal to the server when the application is started and configured to run the video (LAN).
Each client has a small HW module that allows for input of a say 12V signal. The input is polled constantly when the server has signaled via LAN that playing is about to start. This is busy waiting and should thus only take place for a small time interval. The clients need to acknowledge that they are now in polling mode (also over LAN)
After putting the clients into polling mode (including having waited for all of them to acknowledge having done so) the server will send a signal to all clients via some dedicated HW (output 12V signal) over shielded cables which should be all of the same length.
As soon as the polling indicates it, the clients start to play the video and acknowledge that over LAN to the server
Sending a stop signal could also be done via LAN as it is not that critical.
In your scenario you could also have the server broadcast a time stamp over the LAN as all machines are close together differences in latency will be negligible. This would be nifty for all sorts of things one of which being able to decide if a client responded in a timely fashion to a service request by the server.

How about that scenario?

Cheers!