unix network programming!

[aboujouj83]

I am reading unix netwrok programming volume 1 by stevens. It's a known book for network programming. If anyone has this book, I would really appreciate any explanation about the use of the "allset" file descriptor on page 165 figure 6.21.
Thanks
Aboujouj

 

[dickseabrook]

The allset variable appears to be the entire set of descriptors. I will need to study this further, but
the loop on the next page appears to copy allset to
rset, check which of the descriptors on rset may be
ready, and then proceed to open and close descriptors
in allset based on their status, data ready, etc.
The Select() function is only called on rset after it
becomes the current descriptor set through the assignment
rset=allset;
Perhaps this separates maintenance from operations.
Dick S.

 

[aboujouj83]

Thanks! I am waiting for more clarification though.
Aboujouj

 

[Salem]

If you had read the manual page for select(), you will have seen
"On exit, the sets are modified in place to indicate which descriptors actually changed status."

So allset is simply a copy of all the file descriptors which you're interested in. More importantly, it is not modified by calling select().

 

[aboujouj83]

Thanks Salem
Aboujouj