Re: multicast ping

I think your only hope then is to use ICMP. However, machines are not 
obliged to respond to ICMP. The official ping address for hosts is 
224.0.0.1 and for routers 224.0.0.2 IIRC.

Robert Bowen wrote:
> Thanks for your responses. There's a little detail I left out of my 
> last email (because I didn't know it ...) -- these machines that I 
> want to PING are *not* ours. They are machines that our app will send 
> requests to but we don't have any control over them. Which means I 
> can't put a JGroups client on each machine that listens for PINGs and 
> responds.
>
> So I guess I am stuck with Bela's recommendation, to make some "simple 
> multicasting code", without JGroups, because the other recommendations 
> -- using MessageDispatcher.castMessage() or using JGroups with 
> bare-bones.xml -- both require a JGroups client listening on each machine.
>
> So I guess I'll just start searching for plain-old java.net code. :(
>
> This is the second time I've tried to work JGroups into this project 
> and each time, because of project specs, we haven't used it. Bummer.
>
> Thanks,
> Bob
>
> ----- Original Message ----
> From: Bela Ban <belaban@xxxxxxxxx>
> To: Robert Bowen <syg6@xxxxxxxxx>
> Cc: javagroups-users@xxxxxxxxxxxxxxxxxxxxx
> Sent: Tuesday, September 12, 2006 10:10:41 PM
> Subject: Re: [javagroups-users] multicast ping
>
> You could do this with simple multicasting code, or you could use
> JGroups (with the bare-bones.xml config) to simply send out a multicast
> and wait for the first reply. So, no, you don't need to rip out some
> JGroups-internal code and use it in your project, but you could simply
> use a JChannel to do that.
>
> Robert Bowen wrote:
> > Hello all.
> >
> > I've been out of the JGroups loop for a while but diligently perusing
> > the mailing list.
> >
> > I had a question about an app I need to write. What I need to do is,
> > in a given moment send out a multicast "ping" and return the ip of the
> > first machine that answers. I know that internally this is what
> > JGroups does to keep an updated list of "alive" machines. My question
> > is, can I use the same internal mechanism JGroups uses? I don't think
> > so, not without deconstructing the code.
> >
> > The other option is to send out my own multicast message, but if I'm
> > not mistaken, multicast messages don't send back responses.
> >
> > Any thoughts?
>
> -- 
> Bela Ban
> Lead JGroups / Manager JBoss Clustering Group
> JBoss - a division of Red Hat
>
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-- 
Bela Ban
Lead JGroups / Manager JBoss Clustering Group
JBoss - a division of Red Hat


-------------------------------------------------------------------------
Using Tomcat but need to do more? Need to support web services, security?
Get stuff done quickly with pre-integrated technology to make your job easier
Download IBM WebSphere Application Server v.1.0.1 based on Apache Geronimo
http://sel.as-us.falkag.net/sel?cmd=lnk&kid=120709&bid=263057&dat=121642