[485143] Fix detection of broken connections on Windows.

Thanks to Pierre-Yves Boisbunon.

Bug: https://bugs.eclipse.org/bugs/show_bug.cgi?id=485143

ChangeLog.txt

@@ -1,3 +1,6 @@
+Broker:
+- Fix detection of broken connections on Windows. Closes #485143.
+
 Client library:
 - mosq->want_write should be cleared immediately before a call to SSL_write,
   to allow clients using mosquitto_want_write() to get accurate results.

src/loop.c

@@ -56,7 +56,6 @@ extern int run;
 extern int g_clients_expired;
 #endif
 
-static void loop_handle_errors(struct mosquitto_db *db, struct pollfd *pollfds);
 static void loop_handle_reads_writes(struct mosquitto_db *db, struct pollfd *pollfds);
 
 #ifdef WITH_WEBSOCKETS
@@ -322,7 +321,7 @@ int mosquitto_main_loop(struct mosquitto_db *db, mosq_sock_t *listensock, int li
 		fdcount = WSAPoll(pollfds, pollfd_index, 100);
 #endif
 		if(fdcount == -1){
-			loop_handle_errors(db, pollfds);
+			_mosquitto_log_printf(NULL, MOSQ_LOG_ERR, "Error in poll: %s.", strerror(errno));
 		}else{
 			loop_handle_reads_writes(db, pollfds);
 
@@ -437,23 +436,6 @@ void do_disconnect(struct mosquitto_db *db, struct mosquitto *context)
 	}
 }
 
-/* Error ocurred, probably an fd has been closed. 
- * Loop through and check them all.
- */
-static void loop_handle_errors(struct mosquitto_db *db, struct pollfd *pollfds)
-{
-	struct mosquitto *context, *ctxt_tmp;
-
-	HASH_ITER(hh_sock, db->contexts_by_sock, context, ctxt_tmp){
-		if(context->pollfd_index < 0){
-			continue;
-		}
-
-		if(pollfds[context->pollfd_index].revents & (POLLERR | POLLNVAL)){
-			do_disconnect(db, context);
-		}
-	}
-}
 
 static void loop_handle_reads_writes(struct mosquitto_db *db, struct pollfd *pollfds)
 {
@@ -467,6 +449,10 @@ static void loop_handle_reads_writes(struct mosquitto_db *db, struct pollfd *pol
 		}
 
 		assert(pollfds[context->pollfd_index].fd == context->sock);
+		if(pollfds[context->pollfd_index].revents & (POLLERR | POLLNVAL)){
+			do_disconnect(db, context);
+			continue;
+		}
 #ifdef WITH_TLS
 		if(pollfds[context->pollfd_index].revents & POLLOUT ||
 				context->want_write ||