I ran into an issue while doing "Understanding ROS Nodes" tutorial
http://www.ros.org/wiki/ROS/Tutorials/UnderstandingTopics#preview

I noticed that killed ROS nodes are not being removed from "rosnode list".

When I used "rosnode info turtlesim", I saw:
...
contacting node http://i7:*56977*/ ...
ERROR: Communication with node[http://i7:56977/] failed!

I thought maybe it was because I did not have $ROS_HOSTNAME defined as
described here:
http://www.ros.org/wiki/ROS/NetworkSetup#Single_machine_configuration
So I added export ROS_HOSTNAME=localhost

After that "rosnode info turtlesim" give me:
...
contacting node http://localhost:*60372*/ ...
Pid: 6178

I thought it was strange to see a different port number, but rosnode list
started working.

Then I went to the next tutorial and did "roscore" while other roscore was
running.

Then I noticed that  "rosnode list" again doesn't work and "rosnode info
turtlesim" now gives:
contacting node http://localhost:39889/ ...
ERROR: Communication with node[http://localhost:39889/] failed!


P.S. I'm using Fuerte with a fresh Ubuntu-12.04, 64-bit.