Make sure to raise an error on exiting @read_thread

Although an error should be always raised on exiting @read_thread to
break `get` loop, there was a case that it's not raised.

Signed-off-by: Takuro Ashie <[email protected]>

lib/mqtt/client.rb

@@ -271,7 +271,19 @@ def connect(clientid = nil)
         # Start packet reading thread
         @read_thread = Thread.new(Thread.current) do |parent|
           Thread.current[:parent] = parent
-          receive_packet while connected?
+          no_error = true
+          no_error = receive_packet while no_error && connected?
+
+          if no_error
+            # Should not reach here on normal state since `disconnect` kills
+            # this thread, but it will occur when `receive_packet` catches no
+            # error and # `connected?` returns false. An error should be raised
+            # in this case too to break `get` loop.
+            @socket_semaphore.synchronize do
+              close_socket(false)
+            end
+            Thread.current[:parent].raise(MQTT::NotConnectedException)
+          end
         end
       end
 
@@ -469,12 +481,14 @@ def receive_packet
         end
         keep_alive!
       end
+      true
     # Pass exceptions up to parent thread
     rescue Exception => exp
       @socket_semaphore.synchronize do
         close_socket(false)
       end
       Thread.current[:parent].raise(exp)
+      false
     end
 
     def wait_for_puback(id, queue)