ipv6 loopback kepserverex upc ua client

[rexnfx]

Describe the bug

server.conf
tcp_config:
hello_timeout: 5
host: localhost
port: 48050

kepserver ex opc ua client is not compatible with ipv6 loopback for some reason.
[2025-11-14T16:15:56Z INFO opcua_server::address_space] Imported 5118 nodes
[2025-11-14T16:15:56Z INFO opcua_server::server] Try to bind address at [::1]:48050
[2025-11-14T16:15:56Z INFO opcua_server::server] Initializing node managers
[2025-11-14T16:15:56Z INFO opcua_server::server] Now listening for connections on [::1]:48050
[2025-11-14T16:15:56Z INFO opcua_server::server] OPC UA Server: OPC UA Sample Server
[2025-11-14T16:15:56Z INFO opcua_server::server] Base url: opc.tcp://localhost:48050

in kepware i entered the address as both opc.tcp://localhost:48050 and opc.tcp://[::1]:48050 (the latter which kepware would not let me save in the config dialog)

Date Time Level Source Event
11/14/2025 10:29:32 AM Warning OPC UA Client rust | Socket error occurred connecting. | Error = 10061, Details = 'No connection could be made because the target machine actively refused it.'.
Date Time Level Source Event
11/14/2025 10:29:32 AM Error OPC UA Client rust | Channel failed to connect. | Status description = 'Could not establish a network connection to remote server.', Status code = 0X80AC0000.

after changing the serer.conf as follows:
tcp_config:
hello_timeout: 5
host: 192.168.50.15
port: 48050

after setting host to be LAN ip address

tcp_config:
hello_timeout: 5
host: 192.168.50.15
port: 48050

and setting kepware client endpoint url = opc.tcp://192.168.50.15:48050/ everything works as intended.

possible fix being to have option to not use ipv6 loopback for poorly made, but widely used clients. i will also submit a ticket to kepware to have their client updated to allow ipv6 loopback for testing scenarios.

To Reproduce

1. install kepserverex trial
2. create opc ua client channel
3. security policy = None
4. ua server -> endpoint url = opc.tcp://localhost:48050 or opc.tcp://localhost:48050/
5. build "simper-server" from samples
6. use config mentioned above

Expected behavior

Requesting an option to not use ipv6 loopback for localhost

Screenshots

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Version

Python-Version:

opcua-asyncio Version (e.g. master branch, 0.9):