Addition of graceful method to disconnect (#34)

* addition of graceful method to disconnect

* Fix to error grammar

* Change to disconnect output to return null on successful execution

q/mqtt.q

@@ -1,9 +1,12 @@
 \d .mqtt
-connX :`mqtt 2:(`connX;3);
+connX:`mqtt 2:(`connX;3);
 init :`mqtt 2:(`init;1);
 pubx :`mqtt 2:(`pub ;4);
 sub  :`mqtt 2:(`sub ;1);
 unsub:`mqtt 2:(`unsub;1);
+isConnected:`mqtt 2:(`isConnected;1);
+disconnect :`mqtt 2:(`disconnect;1);
+
 
 pub:.mqtt.pubx[;;1;0]
 conn:{[tcpconn;pname;opt]connX[tcpconn;pname](enlist[`]!enlist(::)),opt}

src/mqtt.c

@@ -143,6 +143,28 @@ EXP K connX(K tcpconn,K pname, K opt){
   return (K)0;
 }
 
+/* Disconnect from an mqtt client
+ * timeout = length of time in ms to allow for the client to clean up prior to disconnection
+*/
+
+EXP K disconnect(K timeout){
+  if(!MQTTClient_isConnected(client))
+    return krr((S)"No client is currently connected");
+  else{
+    MQTTClient_disconnect(client,(time_t)timeout->i);
+    MQTTClient_destroy(&client);
+  }
+  return (K)0;
+}
+
+EXP K isConnected(K UNUSED(x)){
+  if(!MQTTClient_isConnected(client))
+    return kb(0);
+  else
+    return kb(1);
+}
+
+
 /* Publish a message to a specified topic
  * topic = topic name as a symbol
  * msg   = message content as a string