Why does my application keep receiving blank messages from PubNub through the REST API even when there is no data?

PubNub sends back an empty keep-alive message (and a time token relative to the last message received from a client) at a certain rate. These messages do not count toward your message usage. You will only see these empty messages (which you can ignore) when using the REST API. You will not see those messages when using the PubNub client SDKs.