rumqtt: Serialization/deserialization error: Max Payload size has been exceeded

[kevchi9]

I can face this issue when I try to read messages on a topic as subscriber, but I can publish them without any problem.
I am also able to read these messages from another subscriber client (e.g. mosquitto subscriber).

I solved this by increasing the max packet size ( set_max_packet_size(MAX_SIZE) ) , in my case the issue happened because the packet was 10791 bytes and the default limit is 10240.

The weird thing is that the error can be encountered with the default configuration, but only as a subscriber.

The messages are json like strings so they have variable length.

[swanandx]

max incoming packet size and max outgoing packet size can be different, and hence it's possible that only incoming packets ( i.e. subscribers ) cause the error.

Can you provide with more information like which version are you using ( like v5? ) to confirm?

[kevchi9]

I'm using v5. Tried with v3 too and had the same issue. So the default packet max sizes are different?

[swanandx]

iirc, broker sends max packet size it can accept in connack and then client adheres to it for max outgoing size.

For v3, to start with we are setting max sizes same ( for both incoming and outgoing ), so not sure, can you share some minimal poc / code to reproduce the behaviour if possible?

Thanks