I am very interested to find out how companies actually create a list of domains that are soon to expire. They must get this information in a cost effective way and I imagine that there it is not a very drawn out ordeal as having to query a list of names to see if any of them are expiring.

So I started searching around google but, obviously, this being a trade secret it's rather difficult to get any good information. What I have come up with so far is that I need to use the Registrar Registry Protocol and issue raw commands to the various TLD servers. Although this is where I think I need to head I can not find any good information on it.

Would anyone be willing to share what they might know? Or help me find a solution?

How about using one of these two scripts? The first one is remotely hosted.

http://www.hotscripts.com/Detailed/30861.html

http://www.hotscripts.com/Detailed/20872.html

Well, I'm looking more for an understanding of how they actually work rather than a premade script. From what I can tell now though they seem to just search through directories and check each domain. This seems to be a rather inneficient method.