Openhabian raberberry how to see Mqtt log in real time

I just intergrade my openhab to raspberry pi 3 with openhabian an i don’t know how to see mqtt server log file n real time.

You can get an mqtt monitor app like mqtt.fx or mqtt-spy and connect to your broker to monitor the traffic. If you subscribe to the topic # you will ALL traffic

ok i did with mqttspy. but i need to see the connections too. not only the topic traffic
thnx in advance

When using mosquitto as mqtt server, the simpe answer is: This is not possible. See for this.
But of course you can take a look at $SYS/broker/clients/connected to get the number of connected clients, and you could start mosquitto from bash by using

mosquitto -v

If setting logging in mosquitto.conf, it’s possible to use a topic for logging, and mqtt spy supports filtering for topics.

i appreciate

Actually, if you set up your config file in /etc/mosquitto/mosquitto.conf and you add the line
log_type all
then restart mosquitto service
service mosquitto restart
you will see everything with
tail -f /var/log/mosquitto/mosquitto.log
Hope it helps