David LeBlanc wrote:
-----Original Message----- From: Damien Miller [mailto:djm@xxxxxxxxxxx] said:
This effectively limits select to a maximum of FD_SETSIZE descriptors
on Windows. I don't think that this limitiation exists on other platforms.
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Note the bit where it says:
#ifndef FD_SETSIZE #define FD_SETSIZE 64 #endif /* FD_SETSIZE */
So to make FD_SETSIZE any arbitrarily large value up to whatever your system can handle, you just redefine FD_SETSIZE before you #include winsock.h.
Something you can't do in linux, is enlarge FD_SETSIZE.
from linux/posix_types/h: #undef __FD_SETSIZE #define __FD_SETSIZE 1024
Well, you *can* change it, but it requires a recompile of the kernel and all userland programs that create an fd_set.
In this regard, windows did get it right. However, the earlier comment on using the windows async sockets is spot on, if you want performance. Windows fd_set's are structured more like unix poll() arrays (un-ordered array of fd's) and are not very efficient if there are many sockets on one set. Also, a linux fd_set limits the fd *value* to < 1024, not just the number of fd's in the set. So it's possible to only want to put one fd on a fd_set but be unable to do so if it's value is > FD_SETSIZE (which can be done by increasing the maximum number of file handles a process is permitted to open).
-lee
