J J said

> >If you want to send one message and have everyone hear it then you have
to use UDP, which is connectionless.


and S.J.Chun asks

> Can you elaborate on this? How could this be done? Any sample code or doc
on this?

J J's referring to sending UDP to multicast addresses. Basically, interested
parties signal (say, through the Internet Group Management Protocol, IGMP
(RFC 2236)) that they want to receive data sent to a particular multicast
address (RFC 3171 defines the (PIv4) multicast address range as 224.0.0.0 to
239.255.255.255. Likely you'd be interested in an address in the
224.0.0.0/24 block, which is for link local multicast.). Datagrams sent to
that multicast address are duplicated and sent to all the interested
parties.

http://en.wikipedia.org/wiki/IP_Multicast is a good starting point for
multicast.

One thing to bear in mind is that any routers between the sender/s and
receiver/s must support multicast.

frank