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The following page has been changed by SteveLoughran:
http://wiki.apache.org/hadoop/ConnectionRefused

The comment on the change is:
page on a commonly seen error

New page:
= 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 [http://www.ietf.org/rfc/rfc793.txt 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
 1. Check the IP address the client gets for the hostname is correct.
 1. Check the port the client is using matches that the server is offering a 
service on.
 1. On the server, try a {{{telnet localhost <port>}}} to see if the port is 
open there.
 1. On the client, try a {{{telnet <server> <port>}}} to see if the port is 
accessible remotely.
 1. Try connecting to the server/port from a different machine, to see if it 
just the single client misbehaving. 

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