My guess from other experience with the Cisco VPN client:
  1. ROS resolved your hostname to an IP, let's call it 192.168.1.15
  2. ROS tries to contact 192.168.1.15 when starting up roscore
  3. VPN client, ever so helpfully, routes ALL network traffic through the tunnel regardless of destination subnet
  4. VPN server end has no idea where to route a message to 192.168.1.15
  5. ROS cannot connect, as the VPN isn't routing requests back to your machine
I'd expect this problem to affect most anything using a VPN that isn't there for the purpose of connecting to a rosmaster.

As you discovered, getting ROS to route things through the loopback interface should bypass the VPN tunnel.

- Eric

On Wed, Sep 15, 2010 at 12:22 PM, Ken Conley <kwc@willowgarage.com> wrote:
FYI: altering an error message is generally not a good idea. In this
case, you're disguising the one piece of information that is useful
for debugging in this case.

This is basically a network configuration problem. Without knowing
what your actual network config is, it's hard to provide a solution.
As a general strategy, network configuration problems are generally
resolved by setting ROS_IP to the IP address of the configuration
you're binding to, or to set ROS_HOSTNAME to a hostname that resolves
correctly across multiple configurations.

 - Ken

On Wed, Sep 15, 2010 at 9:07 AM, trinighost <trinighost@gmail.com> wrote:
>
> Hello Ken,
> I changed the machine name for the post.. but the message does show my
> actual machine name (not localhost).
>
> ROS_MASTER_URI is currently set to.
> http://localhost:11311
>
> The other variables are blank/not set.
> And it doesn't matter whether the machine is on a wired or wireless network.
> --
> View this message in context: http://ros-users.122217.n3.nabble.com/ROS-and-virtual-private-networks-tp1480052p1480777.html
> Sent from the ROS-Users mailing list archive at Nabble.com.
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