[jacquesm]

An active file descriptor is a filedescriptor that you want to read from that has data available and one that you want to write to that has buffer space available.

To put it in another way, if you were to use blocking IO then an operation on an active descriptor would not block. Of course poll and epoll are all about asynchronous IO (so non-blocking by definition) but that's a good way to describe the difference.

Zed's 'superpoll' is precisely what you suggest.

[pmjordan]

Thanks for the explanation, I didn't think of the part about the socket being free for writing vs. whether there was data available.

Zed's 'superpoll' is precisely what you suggest.

Facepalm. Thanks, I mysteriously missed that part of the article.