Winsock: Sending to a Distribution List?

I have an application in mind where I would like to send the same data (5MB - 50MB) to a number of clients over the internet. Since the server connection to the Internet has limited bandwith (512K uplink) and there could be up to 100 clients wanting the same info, I was wondering if there is a more efficient method than direct sends to each client.

1) I'm thinking of a method similar to sending an email to a distribution list, ie. done with a single send.
Is it possible over TCP/IP using VB6 and Winsock (or Winsock API)?
Is it possible to imbed a number of IP addresses into the IP datagram?
Is there anyother way of achieving something like this over the Internet? (Multicast of some sort?)

2) If the clients were logged onto the server via VPN or something, would a Multicast work then?


Cheers,
Nap

Didn't get any comments before, so here's a bump for another try.

I am not sure whether you can do what you described, using the winsock control but if bandwidth is the main issue, than I would suggest you:

1. Try and reduce the amount of data send to each client.

2. Send the data in compressed form using maybe a simple algorithm (such as counting the spaces or repeated characters).

3. Build in restart capabilities so that if a transfer fails, you will not have to send the whole chunk again.

I am not sure if you can change the TCP/IP datagram to put in a list of IP addersses because as with all network carriers, TCP/IP has a specific protocol which need to be adhered to, but maybe someone out there may have succeeded in doing what you have suggested.

Hope this helps.

Franmal, thanks for your comments.

I'm sure there is a way to do it (look at all these video chat applications etc). Just don't know how.

Quote:

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Originally Posted by Napoleon

I'm sure there is a way to do it (look at all these video chat applications etc).

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They send multiple packets. Very wasteful of internet bandwidth, but that's how chat works. Listservers do the same thing - multiple emails.

If you look up MBone and/or mroute in google, you will find some info about Multicasting over the Internet.

A lot of the info you will find is dated as far back as 1998.

Cheers,
Nap