MQTT QoS1 retransmission timeout?

[Jyun-Hao Tang]

This QoS1 ensures that the message arrives at the receiver at least once.

The publisher will retransmit message when it does not receive puback packet.

 

How long does publisher not receive puback packet, it will retransmit message?

thx.

[Nicholas Humfrey]

Hello Jyun,

TCP provides a reliable network transport - so packets should not need
to be re-transmitted while a connection is alive and well.

The only time you need to re-transmit a QoS 1 packet is after a TCP
connection is lost and then re-established.


nick.

> --
> To learn more about MQTT please visit http://mqtt.org
> ---
> You received this message because you are subscribed to the Google
> Groups "MQTT" group.
> To unsubscribe from this group and stop receiving emails from it, send
> an email to mqtt+uns...@googlegroups.com.
> To post to this group, send email to mq...@googlegroups.com.
> Visit this group at https://groups.google.com/group/mqtt.
> For more options, visit https://groups.google.com/d/optout.

[Jyun-Hao Tang]

Hello Nicholas, 

So, if tcp connection is lost, the client republish mqtt qos1 message.

How does mqtt client check if tcp connection is lost? 

The mqtt client library I used is paho mqtt client：https://github.com/eclipse/paho.mqtt.java

I didn't find similar code.

Nicholas Humfrey於 2016年11月7日星期一 UTC+8上午6時45分38秒寫道：

[Nicholas Humfrey]

The client should be notified by the operating system if the TCP
connection to the server has been lost.

TCP can have an issue that dropped connections can not be detected when
no data is being sent. This is one of the reasons for the MQTT clients
sends periodic pings - so that dropped connections can be detected.
Although that shouldn't be an issue if in the middle of a publish flow.

I am not familiar with the Paho Java client. It is perfectly possible
that some implementations don't perform resends on re-connect. My ruby
client doesn't currently support automatic reconnects at all.


nick.

>>> Visit this group at https://groups.google.com/group/mqtt [1].
>>> For more options, visit https://groups.google.com/d/optout [2].

>
> --
> To learn more about MQTT please visit http://mqtt.org
> ---
> You received this message because you are subscribed to the Google
> Groups "MQTT" group.
> To unsubscribe from this group and stop receiving emails from it, send
> an email to mqtt+uns...@googlegroups.com.
> To post to this group, send email to mq...@googlegroups.com.
> Visit this group at https://groups.google.com/group/mqtt.
> For more options, visit https://groups.google.com/d/optout.
>
>

> Links:
> ------
> [1] https://groups.google.com/group/mqtt
> [2] https://groups.google.com/d/optout