Question: I have the following two containers started but kafka says connection refused.

`docker run zookeeper` and `docker run wurstmeister/kafka`

I run it just like that and the connection is refused. In the logs it says:

> 
> INFO Opening socket connection to server localhost/127.0.0.1:2181.
>  Will not attempt to authenticate using SASL (unknown error)
>  (org.apache.zookeeper.ClientCnxn)
> 
> 
> 

then:

> 
> WARN Session 0x0 for server null, unexpected error, closing socket
>  connection and attempting reconnect (org.apache.zookeeper.ClientCnxn)
>  java.net.ConnectException: Connection refused
> 
> 
> 

zookeeper is started first and it on 2181, when starting kafka it looks at 2181 "zookeeper" then blows up on me. Advice?

Answer: 
Hi Drew you need to provide specific zookeeper docker container IP. Instead of localhost in Kafka configuration. You can get Docker IP by running 

> 
> docker ps
> 
> 
> docker inspect 
> 
> 
> 

And you need to make sure that Docker containers are able to communicate with each other. Please refer the following <https://docs.docker.com/engine/userguide/networking/default_network/container-communication/>
Using the Docker 'host' network mode instead of the default 'bridge' mode might help, at least this is the working solution for my project. The 'host' network mode bypasses the IP issue by using the network stack of the Docker host directly instead of creating an isolated Docker network.

As an example see: <https://github.com/mwatzer/kafka-connect-transforms-json-extractor-test/blob/main/docker/kafka/docker-compose.yml>