(Python) how to tell if server listens on a port in use

[sp...@rigetti.com]

In Python, how can find out if the port I'm trying to use for my gRPC server is already in use?  I need to add the port before starting the server, but if I add a port already in use, it starts without any errors.

I'm running Python 2.7 on CentOS 7.

[Nathaniel Manista]

On Fri, Jun 2, 2017 at 12:12 PM, <sp...@rigetti.com> wrote:

In Python, how can find out if the port I'm trying to use for my gRPC server is already in use? I need to add the port before starting the server, but if I add a port already in use, it starts without any errors.

I'm running Python 2.7 on CentOS 7.

I've confirmed your observation.

Did you see any error logging? Possibly something like '"description":"No address added out of total 1 resolved"'?

It looks like the problem is in gRPC Python. The gRPC Core tells us that a return value of zero indicates that the port addition was not successful, but gRPC Python does not examine the Core's return value before passing it to the application. I'm not sure if the right fix is to advertise to applications that a return value of zero indicates a failure or to raise an exception. Which might you prefer?

Thanks for the report,

-Nathaniel

[Nathaniel Manista]

+support list (please retain so that everyone can learn from the conversation)

On Fri, Jun 2, 2017 at 3:01 PM, Spike Curtis <sp...@rigetti.com> wrote:

It doesn't seem to drop any errors.

With the current version, can I do something like?

result = sever.add_secure_port(...)

if result == 0:

    raise PortInUseError()

I haven't yet confirmed this myself but yes, I believe this will work as you need it to work.

-N