Reset the last ping time only after a ping is sent, rather than after… #5
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… any broker command is received. If broker messages are received too frequently, it causes pings to be never sent and the broker disconnecting the client.
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Thank you for the PR, it looks like this could be related to #4. On the one hand, I think the current implementation of the client adheres to the specification as it can be found here for example (see sub-section Keep Alive Timer). On the other hand, I cannot imagine a widely used broker like Mosquitto comes with such a severe bug, since a lot more people and pieces of software would experience issues then. In other words, I'm clueless. I'll have a more thorough look at this tomorrow though, maybe looking for some other specifications. I also used the v3 specification during development, which states the exact same thing as the v3.1 spec. At least that's what I understand from it:
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I also found an article in the HiveMQ blog which interpretes the quoted spec the same way I did. And with HiveMQ the client works fine. I need to investigate this further... |
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I think I understand the problem now. You are subscribing and publishing messages with The problem with that is that even though the client heard from the broker, the broker hasn't heard from the client, since no acknowledgement is being sent. Therefore the broker kills the connection after the configured Keep Alive Interval. In order to fix this, we simply reset the ping timer only when data is sent to the broker, but not when data is received. This is best done in the |
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Thanks a lot for looking into this! Your explanation makes perfect sense and I'm no longer seeing the issue in v0.1.3. |
Using php-mqtt v0.1.2 as a subscriber, and mosquitto v1.4.15 as the broker:
Whenever the client receives a command from the broker, it resets its internal "last ping" time. If these commands are received frequently enough, the "last ping" time never exceeds the keepalive value, so pings are never sent, causing the broker to report the client has timed out and close the connection. I get a message like this in the mosquitto log:
And the client throws an exception soon after:
Not having read the MQTT spec, I don't know if this is a bug in the client or the broker. I was able to fix it by only resetting the last ping time after a ping is sent, rather than after every broker command is received.