launch_gateway and IPv6-only localhost not possible

[erl987]

Hi,

it does not seem to be possible to launch the Java-side process through launch_gateway and having it listening on an IPv6 localhost address. Digging into the code base, it looks like GatewayServerBuilder is setting the IPv4 address 127.0.0.1 by default. This class is used by launch_gateway but it lacks an option to change the IP-address - or at least the IP-version.

It is actually possible to run py4j on an IPv6 localhost by using a main method such as in ExampleIPv6Application. But unfortunately, we need to use launch_gateway for robust startup of the Java-side process on all platforms.

Did I miss here something, i.e. is there any way to make IPv6 connections possible with launch_gateway.

IPv6 is becoming a hot topic since the US-government controlled IT systems are required to be migrated soon to IPv6-only networks (while it is a bit unclear if this also affects the localhost).

I believe that it would be rather simple to adapt launch_gateway to make it work with a IPv6-only localhost address. I could contribute a pull request if wished.

/Ralf