Connection Refused

You get a ConnectionRefused Exception when there is a machine at the address specified, but there is no program listening on the specific TCP port the client is using -and there is no firewall in the way silently dropping TCP connection requests. If you do not know what a TCP connection request is, please consult the specification.

Unless there is a configuration error at either end, a common cause for this is the Hadoop service isn't running.

1. Check the hostname the client using is correct
2. Check the IP address the client gets for the hostname is correct.
3. Check the port the client is using matches that the server is offering a service on.

4. On the server, try a telnet localhost <port> to see if the port is open there.

5. On the client, try a telnet <server> <port> to see if the port is accessible remotely.

6. Try connecting to the server/port from a different machine, to see if it just the single client misbehaving.

None of these are Hadoop problems, they are host, network and firewall configuration issues. As it is your cluster, only you can find out and track down the problem.