libevent http client with request timeout - c

Question

I am using libevent to get some stats of a web site in certain time intervals. I've based the program on this. The only thing I'm missing is a timeout on the request, preferably in subsecond accuracy.
I've tried a few things, but couldn't get it to work. I'd really appreciate any pointers on this.

Answer 1

This is a very crude example: I've used libevent timers to implement the timeout. This could be further improved by putting the timer in the struct and cancelling it in the callback.
#include <stdio.h>
#include <event.h>
#include <evhttp.h>
#include <stdlib.h>
#include <unistd.h>
struct http_client {
struct evhttp_connection *conn;
struct evhttp_request *req;
bool finished;
};
void _reqhandler(struct evhttp_request *req, void *state) {
struct http_client *hc = (http_client*)state;
hc->finished = true;
if (req == NULL) {
printf("timed out!\n");
} else if (req->response_code == 0) {
printf("connection refused!\n");
} else if (req->response_code != 200) {
printf("error: %u %s\n", req->response_code, req->response_code_line);
} else {
printf("success: %u %s\n", req->response_code, req->response_code_line);
}
event_loopexit(NULL);
}
void timeout_cb(int fd, short event, void *arg) {
struct http_client *hc = (http_client*)arg;
printf("Timed out\n");
if (hc->finished == false){ // Can't cancel request if the callback has already executed
evhttp_cancel_request(hc->req);
}
}
int main(int argc, char *argv[]) {
struct http_client *hc = (struct http_client *)malloc(sizeof(struct http_client));
hc->finished = false;
struct event ev;
struct timeval tv;
tv.tv_sec = 3; // Timeout is set to 3.005 seconds
tv.tv_usec = 5000;
const char *addr = "173.194.39.64"; //google.com
unsigned int port = 80;
event_init();
hc->conn = evhttp_connection_new(addr, port);
evhttp_connection_set_timeout(hc->conn, 5);
hc->req = evhttp_request_new(_reqhandler, (void*)hc);
evhttp_add_header(hc->req->output_headers, "Host", addr);
evhttp_add_header(hc->req->output_headers, "Content-Length", "0");
evhttp_make_request(hc->conn, hc->req, EVHTTP_REQ_GET, "/");
evtimer_set(&ev, timeout_cb, (void*)hc); // Set a timer to cancel the request after certain time
evtimer_add(&ev, &tv);
printf("starting event loop..\n");
printf("\n");
event_dispatch();
return 0;
}