I'm facing this problem when I have installed Apache Storm on two machines on AWS EC2 Amazon
storm list
Running: java -client -apache-storm-0.9.4/bin backtype.storm.command.list
53149 [main] INFO backtype.storm.thrift - Connecting to Nimbus at 172.31.32.97:6627
Exception in thread "main" org.apache.thrift7.transport.TTransportException: java.net.ConnectException: Connection refused
The problem was Nimbus could not connect with Zookeeper nodes on other machines due to the ports of Nimbus and Zookeeper were not opened .The security was the problem on the machines and the port 2181 of Zookeeper was closed on machines. I solved the problem by setting the ports of Nimbus and zookeepers are open. If you need more description about the answer, just write comment.