NNTP and the GROUP command

[Thomas Tierney]

Does anyone understand this command? the RFC States
CLIENT : GROUP this.newsgroupgroup.news
SERVER : 211 <n> <f> <l> this.newsgroupgroup.news

Where n = estimated number of articles
f = first article
l = last article

No matter where I look, I can not tell if article f+1 will always be the same article. What I want to do is download news but not the same articles, only new onces since the last time I downloaded. the NEWNEWS command will do this but it is really only supported on what ever newserver has enabled it and there are not that many.

Any help would be greatly appreciated

Thanks

[Mike Stefanik]

Generally speaking, the article numbers should increment in the way that you expect. For example, let's say the first time that you visit a group, the first article is 10912 and the last article is 11847. A few days later, the first article changes to 11049 and the last article is 13941 (new messages have been added, old messages have expired). In both cases, article 11845 should refer to the same article. The one thing that you can't guarantee is that every article number will be consecutive; there may be "gaps" in the range of available articles, and your client needs to expect this.

That said, you cannot be absolutely certain that article numbers will be consistent over time. The server administrator may reorder the database for the newsgroup, etc. So, using the above example, let's say you wanted to pick up all of the new posts. The last known news article you have is 11847, and new ones are 11848 (the first new article) through 13941. What you can do is download 11847 again, and compare the Message-ID header with the value that you've stored from the last time you pulled down messages. If they match, then it's safe to presume that you can start with the new messages at 11848. If its message ID doesn't match, then that means 11847 doesn't refer to the same article that it did a few days ago; something has changed with the numbering, and at that point you need to punt and download the complete list of messages and resync your local database so that it matches the server.

[Thomas Tierney]

It is baffling that the RFC would make it inconsistent. I do understand now and thanks for the help