Can not connect to kafka brokers but zookeepers are still

My msk service are running well until recently kafka brokers cannot be connected but zookeepers are still connected successfully.

I also double checked VPC, It's same. Eventually restart all brokers

I tried these commands below

telnet broker_dns_1 9092  
#=> Trying ip...  
telnet: Unable to connect to remote host: Connection refused  
  
telnet zookeeper_dns_1 2181  
#=> Trying ip...  
connected to zookeeper_dns  

Because response of telnet broker_dns command are so fast, I guess they can be blocked by some rules. have you guys encountered this issue or known the root cause ?

Edited by: taisytran on Jan 17, 2021 8:50 PM

Edited by: taisytran on Jan 17, 2021 8:50 PM