...
/* Initialize the input set */
FD_ZERO(&input);
FD_SET(fd, &input);
FD_SET(sock, &input);
max_fd = (sock > fd ? sock : fd) + 1;
/* Do the select */
n = select(max_fd, &input, NULL, NULL, NULL);
/* See if there was an error */
if (n < 0)
perror("select failed");
else if (n == 0)
puts("TIMEOUT");
else
{
/* We have input */
if (FD_ISSET(fd, &input))
process_fd();
if (FD_ISSET(sock, &input))
process_socket();
}
I am wondering wouldn t this approach exit out as soon as one of the descriptors is ready.
What if I want to read both the descriptors?
I still want to use select(...) to figure out which is ready first to be processed first.
I tried putting the whole thing in a loop, but then it blocks forever.
最新更新
328 fd_set readfds; FD_ZERO(&readfds);
329 int waiting = 2;
330 while(waiting) {
331
332 FD_SET(sockv4query, &readfds);
333 FD_SET(sockv6query, &readfds);
334
335 /* one greater than the highest fd number */
336 int nfds = (sockv4query > sockv6query ? sockv4query : sockv6query) + 1;
337
338 if (
339 select(
340 nfds, /* number of fds */
341 &readfds, /* set of read fds */
342 NULL, /* set of write fds */
343 NULL, /* set of exception fds */
344 NULL /* maximum wait interval */
345 ) < 0
346 ) {
347 perror("select(...)");
348 continue;
349 } else {
350
351 /* one or more descriptors is ready */
352 if(FD_ISSET(sockv4query, &readfds)) {
353 receive_response_and_echo(sockv4query);
354 waiting -= 1;
355 }
356 if(FD_ISSET(sockv6query, &readfds)) {
357 receive_response_and_echo(sockv6query);
358 waiting -= 1;
359 }
360 }
361 }