Talking to keycloak from a docker deployed app

I have:

keycloak deployed locally on localhost:8080
I have enabled my URL on the client localhost:8082
spring boot app talking to keycloak deployed locally on localhost:8082
I call out for an access_token from app to keycloak and all is well

When I deploy my local app in a docker container I am being refused access with connection refused errors
my docker app is mapped to port 8082 as you might expect
I am using host.docker.internal instead of localhost as advised

Why am I getting connection refused errors?

Any help much appreciated :frowning: