why this "kqueue()" tcp server hangs unexpectedly? - c++

Question

So i'm trying to create a minimal tcp server using kqueue, assuming all the previous details of socket(), bind(), listen() is working correctly given that i've tested them using a thread-per-connection model. why it hangs unexpectedly ?
struct kevent events;
struct kevent change_list;
// create a kqueue
int kq = kqueue();
if (kq < 0) {
throw KqueueException();
}
// initialize the events we want to monitor
EV_SET(&events, sock, EVFILT_READ, EV_ADD, 0, 0, NULL);
// monitor the events
if (kevent(kq, &events, 1, NULL, 0, NULL) < 0) {
throw KqueueException();
}
int nev;
while (true) {
// wait for events to happen
nev = kevent(kq, NULL, 0, &change_list, 1, NULL);
if (nev < 0) {
throw KqueueException();
}
else if (nev > 0) {
// if the event fd is the same as the socket fd we have a new connection
if ((int)change_list.ident == sock) {
std::cout << "new connection" << std::endl;
// accept the connection
int client_fd = accept(sock, NULL, NULL);
if (client_fd < 0) {
throw AcceptException();
}
// add the new connection to the events we want to monitor
EV_SET(&events, client_fd, EVFILT_READ, EV_ADD, 0, 0, NULL);
// add the new connection to the events we want to monitor
if (kevent(kq, &events, 1, NULL, 0, NULL) < 0) {
throw KqueueException();
}
}
else if (change_list.filter == EVFILT_READ) {
char hello[] = "HTTP/1.1 200 OK\nContent-Type: text/plain; charset=UTF-8\nContent-Length: 15\n\nhello from meee\n";
send(change_list.ident, hello, strlen(hello), 0);
}
}
}
using a browser i entered localhost:8090 and the program entered the
if ((int)change_list.ident == sock) {...
the first time and then accepted the connection, went to next iteration and entered the second if condition else if (change_list.filter == EVFILT_READ) {.. (these two actions happened and i received a hello message in the browser ) but when i refreshed the browser the server just hangs with no error (which means no exceptions happen). i tried debugging and it seems like the program keeps entering the else if (change_list.filter == EVFILT_READ) {.. condition over and over until it hangs,I tried adding (naively) nev = 0 at each end of iteration to reset the events count which surely didn't resolve the problem, am i doing something wrong... ? can u give an explanation to what's happening ?