Process incoming packet first in loop()

[arkusuma]

Hi Nick,

I'm writing a GPRSClient. I've got a case where I can only call PubSubClient::loop() after a long operation (GPRSClient::write() with timeout of 30 seconds, way beyond MQTT_KEEPALIVE). On that period a MQTT packet came (PingResp in this case). When I finally call PubSubClient::loop() it disconnect the connection because of PingOutstanding timeout, even though the packet is there in GPRSClient RX buffer. This patch fix that problem by handling incoming packet first before checking for timeout.

Regards,
Anugrah

[knolleary]

The keepalive timer works both ways. If your client is not going to respond to a ping for longer than the keepalive interval, you are at risk of the server timing you out.

For your scenario, the correct solution is to increase the value of MQTT_KEEPALIVE to be bigger than any other timeout you have that may prevent the client from responding to a ping.