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: 
Had the same issue. What helped was actualy:

1. Creating a bridge network: `docker network create -d bridge kafka-network`
2. Running a Zookeeper within this network: `docker run -d -p 2181:2181 --network kafka-network --name zookeeper zookeeper:latest` along with exposing port `2181`
3. Running a Kafka docker attaching it to the network and using Zookeeper's container name as a host: `docker run -d -e KAFKA_ZOOKEEPER_CONNECT=zookeeper:2181 -e KAFKA_ADVERTISED_LISTENERS=PLAINTEXT://localhost:9092 -p 9092:9092 --network kafka-network --name kafka confluentinc/cp-kafka:latest`
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>