How to setup MQTT broker for read/write data via MQTTPUB/MQTTSUB block on Altair Activate

I try to send/receive data via MQTTPUB and MQTTSUB with mqtt example file in Activate 

MQTT broker that I use is mosquitto broker 

When I run example to publish and subscribe data, then the error will occur that "Connection Refused: identifier rejected".

On Broker say that "Bad socket read/write on client MQTTPUB: Invalid arguments provided."

I don't know why and how to solve it.

Could you please tell me why this problem occur and how to setup mosquitto mqtt broker to solve this problem?