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From: Bill Cunningham on 2 May 2010 12:53
#include "main.h"
#include <sys/poll.h>

static struct pollfd po[1];
static struct addrinfo ad, *p;
static int sock, con;
static char buf[1024] = "hello world";

int client(char *ip, char *port)
{
ad.ai_family = PF_INET;
ad.ai_socktype = SOCK_STREAM;
getaddrinfo(ip, port, &ad, &p);
sock = socket(p->ai_family, p->ai_socktype, 0);
fcntl(sock, F_SETFL, O_NONBLOCK);
connect(sock, p->ai_addr, p->ai_addrlen);
po[0].fd = sock;
po[0].events = POLLOUT | POLLERR;
con = poll(po, 2, 3500);
if (con == 0) {
puts("time out err");
return 1;
}
if (po[1].revents & POLLERR) {
perror("poll error");
return -1;
}
if (po[1].revents & POLLOUT) {
send(sock, buf, strlen(buf) + 1, 0);
puts("success");
return 0;
}
send(sock, buf, strlen(buf) + 1, 0);
puts("success");
return 0;
}

For some reason this code never makes it to the IF that allows for send.
The last send send's correctly to the ip that I input. Should I use
continues in those IFs that are above the one that sends?

if (po[1].revents & POLLOUT) {
send(sock, buf, strlen(buf) + 1, 0);
puts("success");
return 0;

The code never makes it to here. This is probably a C syntax question.

Bill



From: Rainer Weikusat on 2 May 2010 13:01
"Bill Cunningham" <nospam(a)nspam.invalid> writes:

[...]

> static struct pollfd po[1];

This is the same as

static struct pollfd po;

[...]

> if (po[1].revents & POLLERR) {
> perror("poll error");
> return -1;
> }
> if (po[1].revents & POLLOUT) {
> send(sock, buf, strlen(buf) + 1, 0);
> puts("success");
> return 0;
> }

po[1] is the same as *(po + 1) which would access the second element
of the array po. But your array has only one element.
From: Bill Cunningham on 2 May 2010 14:43
Rainer Weikusat wrote:

> po[1] is the same as *(po + 1) which would access the second element
> of the array po. But your array has only one element.

Oh yeah that's it. I was thinking wrongly then about the IF's. Thanks.

Bill


From: Bill Cunningham on 3 May 2010 14:27
> Rainer Weikusat wrote:
>
>> po[1] is the same as *(po + 1) which would access the second element
>> of the array po. But your array has only one element.

I changed the code to static struct pollfd *po;

and renamed the arrays po[0] and re-compiled and got a smooth compilation.

Bill


From: Rainer Weikusat on 3 May 2010 15:26
"Bill Cunningham" <nospam(a)nspam.invalid> writes:
>> Rainer Weikusat wrote:
>>
>>> po[1] is the same as *(po + 1) which would access the second element
>>> of the array po. But your array has only one element.
>
> I changed the code to static struct pollfd *po;
>
> and renamed the arrays po[0] and re-compiled and got a smooth
> compilation.

This should result in a segfault at runtime because you are now trying
to derefences a null pointer. You need to declare a structure, not a
pointer to a structure. And access the revents-member like this:

po.revents

NB: This is only true for a single struct pollfd, as in your example.
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