I have a single node, multi (3) broker Zookeeper / Kafka setup. I am using the Kafka 0.10 Java client.
I wrote following simple remote (on a different Server than Kafka)
I encounter the same problems.
You should change your kafka server.properties to specify ip address. eg:
PLAINTEXT://YOUIP:9093
if not, kafka will use hostname, if the producer can not get the host, it can not send message to kafka even if you can telnet them.