[IPython-dev] ConnectionRefusedError when trying to start ipengines

[Fernando Perez]

Hi Anand,

On Jan 10, 2008 2:21 PM, Anand Patil <anand.prabhakar.patil at gmail.com> wrote:
> Hi all,
>
> Has anyone seen an error like this when trying to start an ipengine?
> Possibly useful information: I have denyhosts running but can ssh to my own
> machine without getting blocked.

First question: is the controller already running?  And on the same
machine?  Because you aren't telling the engine where to find the
controller, so it will look for it on the same host. That error means
the engine can't connect to the controller.

If not, are the engine and the controller on the same subnet?  Is the
controller running a firewall? The engine tries to connect to the
controller, by default, on ports > 10000, though you can control this
via:

ipcontroller --engine-port=10001              # listen on 10001
ipengine --controller-port=10001              # connect to 10001

as indicated in

http://ipython.scipy.org/moin/Parallel_Computing/Tutorial

But it's possible that either a firewall on your controller, or
tcpwrappers, is blocking access to those ports from anything but
localhost.

One thing you can try is to make the 'cluster' entirely local to the
controller, by running on it

ipcluster -n 2

That will make one controller and two engines on the same box, and
will sort out if connections to that port are only being blocked when
coming from outside of localhost.  In fact, once it's running, you can
try adding another engine to it.

Let us know if this helps any...

Cheers,

f