title: publishing message to external Kafka Broker from docker container
body: <p>In my IDE, I am able to utilize a spring-boot application that would produce message(with Kafkaproducer) to an external kafka broker. But once I have hosted my spring-boot application in docker container, my application can no longer submit to the broker.
  Here is the error message:</p>
  
  <pre><code>    o.s.k.support.LoggingProducerListener: Exception thrown when sending a message with key='null' and payload='....' to topic Category: 
  org.apache.kafka.common.errors.TimeoutException: Failed to update metadata after 60000 ms.
      org.springframework.kafka.core.KafkaProducerException: 
  Failed to send; nested exception is org.apache.kafka.common.errors.TimeoutException: Failed to update metadata after 60000 ms.
  </code></pre>
  
  <p>what I used to run docker was: <code>docker run -p 9001:9001 -d image_name</code> in which 9001 is my spring-boot port, I am able to Post to the port, just that once my message was posted, it won't get to the external broker.
  I think I have the general concept that Docker containers are living in isolated land where you have to open/map the port in order to access it(like my -p 9002:9002), but does it work the same way to access out from container? if so, can someone please show me how I can run the docker container in order to be able to access to the external broker(let's say the broker URL is "192.168.1.1:9000")? I don't think I am able to modify anything on the broker now, but my assumption is that if I can access via my IDE, why not in docker? Thanks for all the help!</p>