GCN-XML and Dakota

[John Swinbank]

Hi Roy,

On 25 Jan 2012, at 17:33, Roy Williams wrote:

> -- Each uses the uncommon idea that the receiver of the message initiates the connection (usually the sender connects).

Regardless of whether we regard that as "uncommon" or not, I'm not actually sure that it's correct.

What you describe is certainly true or the vTCP protocol. However, my understanding is that the GCN system is the reverse. To quote (from the comments in xml_sock_demo.c):

> To do this GCN needs to be the "client" end.  If your "server" end is running,
> the GCN "client" will connect to it and send the various XML_packets (imalives
> and burst types).


GCN is able to do this because they maintain a "sites.cfg" file which lists all the subscribers to connect to. In the vTCP case, such a file is unnecessary: modulo administrative restrictions, any subscriber can connect and start receiving events with no additional configuration at the sender.

By the way:

> I am trying to understand the difference between GCN-XML [1][2] and Dakota [3][4]

Although the Dakota Tools make for an excellent reference implementation for the vTCP system, I don't think there's anything Dakota specific about it. Certainly, the spec is self contained and easy to implement without reference to Dakota.

Cheers,

John