Windows application listens on IPv4 but not IPv6 UDP

Question

I have setup a Windows Server 2022 AWS EC2 instance. I installed and am testing an application that only runs on Windows.

When setting up the EC2 instance I enabled both IPv4 and IPv6. AWS requires IPv4, and my computer only has a IPv4 IP address (WAN).

However, the software is only listening on the IPv4 address and not the IPv6 address. (checked using 'netstat -aon').

I am using 2 ports. One is a TCP port and the other is UDP (both with different port numbers).

I need to test the incoming connection with IPv6 only.

Since it was only listening on IPv4, I used PortProxy on the Windows server to map the IPv6 IP to the IPv4 IP.

netsh interface portproxy add v6tov4 listenaddress=:: listenport=1234 connectaddress=127.0.0.1 connectport=1234

This now mapped the incoming data from a IPv6 address (such as a remote IPv6 connection) and proxy it to the IPv4 IP address (internally) and it worked fine.

However when I do the same for UDP it doesn't work. From my research UDP doesn't work with PortProxy.

Anyone know how I can proxy UDP from an IPv6 to an IPv4 IP?

Or, how can I do it natively without using a proxy? Is it the software that is causing the port to only listen on IPv4 (the software company who wrote the software need to enable IPv6 in there code), or is it something I have done on the server to cause it to not to listen on IPv6?

Answer 1

Check the AWS docs how to assign a IPv6 address to an interface and to check if it has an IPv6

https://docs.aws.amazon.com/AWSEC2/latest/WindowsGuide/using-instance-addressing.html#working-with-ip-addresses

Assign an IPv6 address to an instance If your VPC and subnet have IPv6 CIDR blocks associated with them, you can assign an IPv6 address to your instance during or after launch. The IPv6 address is assigned from the IPv6 address range of the subnet, and is assigned to the network interface with the device index of eth0. To assign an IPv6 address during instance launch Follow the procedure to launch an instance, and when you configure Network Settings, choose the option to Auto-assign IPv6 IP