Gordon Messmer wrote:
Howard
Wilkinson wrote:
I wanted to add a socketpair connection from
the master process to the servers which implement the actual
functionality. I created the socketpair, set both ends non-blocking and
added it to the select set of fd's. I get an immediate return saying
that the socket is ready to read but when I issue a recv I get -1
(EAGAIN). Nothing I have tried sets the required behaviour of only
returning when there is 'real' data to read.
You're probably better off asking on a Posix programming list than
here. Wherever you ask, though, you should post the code in question,
or code that demonstrates the problem in a state that can be compiled
and verified by others. While you've described what you think you've
done, you haven't given enough information for us to do anything but
guess at the problem.
Can you suggest such a list - I can only find lists for POSIX threads!
Code goes as follows
int fd[2] = { -1, -1 };
fd_set rfd;
int rv;
char buf[1024];
struct timeval timeout = { 10, 0 };
rv = socketpair(PF_UNIX, SOCK_DGRAM, 0, fd);
if (rv < 0) Err("socketpair");
fcntl(fd[0], F_SETFL, fcntl(fd[0], F_GETFL, 0) | O_NONBLOCK);
FD_ZERO(rfd);
FD_SET(fd[0], rfd);
rv = select(fd[0]+1, &rfd, NULL, NULL, &timeout);
if (FD_ISSET(fd[0], rfd)) {
printf("Socket is ready to read\n");
rv = recv(fd[0], buf, sizeof(buf), MSG_DONTWAIT);
if (rv < 0) Err("recv - %s(%d)", strerror(errno), errno);
printf("Socket returned %d bytes\n", rv);
} else {
printf("Socket is not ready to read\n");
}
exit (0);
I contend that this should (if I understand the semantics correctly)
print out "Socket not ready to read" instead I get "recv - Resource
temporarily unavailable(11)"
Anybody?
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