Thread: using select with sockets.

exert from code: (just the essencial)

Code:

fd_set fdset,fdsetbck;

FD_ZERO(&fdsetbck);
FD_SET(sfd,&fdsetbck);
(sfd is a tcp sockect, after listen instruction)
while(1){
 memcpy(&fdset,&fdsetbck,sizeof(fdsetbck));

 select(maxfd+1, &fdset, NULL, NULL, NULL);

 if (FD_ISSET(sfd,&fdset)){
 if((newfd=accept(sfd,(struct sockaddr*)&addrs,&addrlens))==-1) ....
 FD_SET(newfd,&fdsetbck);
if (newfd>maxfd) maxfd=newfd;

 add newfd to descriptors array
 ...
for cycle testing array of descriptors
 if (FD_ISSET(array[n],&fdset))
}
}

my ideia is: each time there is a new connection on the socket a new file descriptor is created and added to the file set. that way if i get a message on the file descritpr used in listen or any of the ones created before i can read from it.

the problem is: when i get the 1st connection on sfd, newfd is created and i can read from it, and add it to the fdset. when it enters 2 loop, the (FD_ISSET(sfd,&fdset)) condition is true again, when i know there was no connections on sfd.
am understanding this wrong, of do i have to flush, or clean, or something like that, sfd, so that select doesn´t think there is a new connection on it?

tks

It's been a while since I've done this, but you should be calling select on your set of descriptors, not just on INT_MAX.


Quzah.

When in doubt, call Beej: Beej's Guide to Network Programming


Quzah.