Re: Detecting server on lan

From:

Knute Johnson <nospam@rabbitbrush.frazmtn.com>

Newsgroups:

comp.lang.java.programmer

Date:

Thu, 02 Jul 2009 09:09:26 -0700

Message-ID:

<4a4cdbb6$0$24098$b9f67a60@news.newsdemon.com>

Ken T. wrote:

On Wed, 01 Jul 2009 21:28:57 -0700, Knute Johnson wrote:

Ken T. wrote:

I would like to have the client detect a server on a lan. So there
will be some 30 clients on the same lan as a single server and when
they start I want them to be able to find the server and automatically
connect to it for using RMI.

My idea was to have them send out a UDP packet to the broadcast address
and then have the server respond saying, "Here I am!", but I'm having
difficulty figuring out how to send a UDP packet to the broadcast
address of the lan.

I tried just sending it to "255.255.255.255", but this didn't work. Is
there a way to detect the broadcast address? Is there a way to send a
packet to it? Is there a simpler way to do what I'm trying to do?

Thanks.

You can't just try to connect to the server?

That's the thing.. I don't know its IP address. I want to detect it.

OK, I understand what you are asking now. The UDP packet idea sounds
pretty simple. Just have the server broadcast to a specific address and
port with its IP address. The clients can read the UDP packets and
connect to the sent address. There is a range for multicast addresses,
take a look at the class MulticastSocket. It has all the details and if
you know how to do UDP datagrams in Java you should be good to go.

--

Knute Johnson
email s/nospam/knute2009/

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