<<TableOfContents(3)>>

== ERROR: Unable to communicate with master! ==
'''Example:'''
 {{{
rosnode ping rosout
rosnode: node is [/rosout]
ERROR: Unable to communicate with master!
 }}}

'''Solution: ''' 
 * Is your [[Master]] running? If no, please run `roscore`
 * Is your `ROS_MASTER_URI` set correctly? If no, please set the `ROS_MASTER_URI` tothe location of your [[Master]].
 * Can you contact the address specified in the `ROS_MASTER_URI`? {{{
$ echo $ROS_MASTER_URI
http://foo:11311
$ ping foo
ping: unknown host foo
}}} If you get the "unknown host" error, please check your network settings or change the `ROS_MASTER_URI` to a resolvable address.

== rosnode machine doesn't find all nodes on a machine ==

The machine name argument to `rosnode machine` must resolve to the same address as the machine reports. Thus "localhost" probably will ''not'' match local nodes. 

You can determine the address a node is using by running `rosnode info <node-name>`:{{{
$ rosnode info rosout
--------------------------------------------------------------------------------
Node [/rosout]

... stuff you can ignore ...

contacting node http://foo:46621/ ...
}}}

In the above example, the machine name is "foo".