Fix websockets clients sometimes not being disconnected promptly.

Closes #1718. Thanks to Luca Casonato.

ChangeLog.txt

@@ -11,6 +11,8 @@ Broker:
   set to true. Closes #1729.
 - Fix `autosave_interval` not being triggered by messages being delivered.
   Closes #1726.
+- Fix websockets clients sometimes not being disconnected promptly.
+  Closes #1718.
 
 Client library:
 - Improved documentation around connect callback return codes. Close #1730.

src/websockets.c

@@ -302,7 +302,10 @@ static int callback_mqtt(struct libwebsocket_context *context,
 				}
 				count = libwebsocket_write(wsi, &packet->payload[packet->pos], txlen, LWS_WRITE_BINARY);
 				if(count < 0){
-					if (mosq->state == mosq_cs_disconnect_ws || mosq->state == mosq_cs_disconnecting){
+					if (mosq->state == mosq_cs_disconnect_ws
+							|| mosq->state == mosq_cs_disconnecting
+							|| mosq->state == mosq_cs_disused){
+
 						return -1;
 					}
 					return 0;
@@ -313,7 +316,10 @@ static int callback_mqtt(struct libwebsocket_context *context,
 				packet->to_process -= count;
 				packet->pos += count;
 				if(packet->to_process > 0){
-					if (mosq->state == mosq_cs_disconnect_ws || mosq->state == mosq_cs_disconnecting){
+					if (mosq->state == mosq_cs_disconnect_ws
+							|| mosq->state == mosq_cs_disconnecting
+							|| mosq->state == mosq_cs_disused){
+
 						return -1;
 					}
 					break;
@@ -340,7 +346,10 @@ static int callback_mqtt(struct libwebsocket_context *context,
 
 				mosq->next_msg_out = mosquitto_time() + mosq->keepalive;
 			}
-			if (mosq->state == mosq_cs_disconnect_ws || mosq->state == mosq_cs_disconnecting){
+			if (mosq->state == mosq_cs_disconnect_ws
+					|| mosq->state == mosq_cs_disconnecting
+					|| mosq->state == mosq_cs_disused){
+
 				return -1;
 			}
 			if(mosq->current_out_packet){