Fix mosquitto_sub being unable to terminate with Ctrl-C.

This occured if a successful connection was not made.

Closes #1957. Thanks to Peoh.

ChangeLog.txt

@@ -4,6 +4,10 @@ Broker:
 - Fix LWT not being sent on client takeover when the existing session wasn't
   being continued. Closes #1946.
 
+Clients:
+- Fix mosquitto_sub being unable to terminate with Ctrl-C if a successful
+  connection is not made. Closes #1957.
+
 Apps:
 - Fix `mosquitto_passwd -b` using username as password (not if `-c` is also
   used). Closes #1949.

client/sub_client.c

@@ -45,13 +45,18 @@ struct mosquitto *mosq = NULL;
 int last_mid = 0;
 static bool timed_out = false;
 static int connack_result = 0;
+bool connack_received = false;
 
 #ifndef WIN32
 void my_signal_handler(int signum)
 {
 	if(signum == SIGALRM || signum == SIGTERM || signum == SIGINT){
+		if(connack_received){
 			process_messages = false;
 			mosquitto_disconnect_v5(mosq, MQTT_RC_DISCONNECT_WITH_WILL_MSG, cfg.disconnect_props);
+		}else{
+			exit(-1);
+		}
 	}
 	if(signum == SIGALRM){
 		timed_out = true;
@@ -123,6 +128,8 @@ void my_connect_callback(struct mosquitto *mosq, void *obj, int result, int flag
 	UNUSED(flags);
 	UNUSED(properties);
 
+	connack_received = true;
+
 	connack_result = result;
 	if(!result){
 		mosquitto_subscribe_multiple(mosq, NULL, cfg.topic_count, cfg.topics, cfg.qos, cfg.sub_opts, cfg.subscribe_props);