Prometheus C# 6 dotnet - connection refused in Docker - docker

Question

I am trying to get a .net C# 6 API to remove metrics through to Prometheus, both running inside docker containers.
When I visit http://localhost:9090/targets, it is telling me that "Get "http://myapi:50505/metrics": dial tcp 192.168.65.2:50505: connect: connection refused" (the state is Down).
Within my api container, I did a netstat --tcp --listen --numeric-ports expecting that port 50505 would be being listened to, but it wasn't -- just 5005 (and 35605, which I also tried in the prometheus.ym).
I tried adding "50505:50505" to the ports on myapi.
One Google search suggested my C# 6 code should do this:
var metricServer = new KestrelMetricServer(port: 1234);
metricServer.Start();
So I did that, changed the prometethus.yml to listen for port 1234, still no luck.
I've tried the suggestions out there, including using localhost:50505 in the prometheus.yml, exposing 50505 in my API Dockerfile.
No errors in either the myapi nor prometheus logs.
No luck.
This is my prometheus.yml:
global:
scrape_interval: 15s
scrape_configs:
- job_name: "myapi"
scrape_interval: 5s
static_configs:
- targets: ["myapi:50505"]
This is my docker-compose.yml
version: '3.3'
services:
myapi:
image: myapi
container_name: myapi
ports:
- "7109:5005"
networks:
- mynet
prometheus:
image: prometheus
ports:
- "9090:9090"
depends_on:
- myapi
networks:
- mynet
networks:
mynet:
driver: bridge
I built the prometheus container with this Dockerfile
FROM prom/prometheus
ADD ./prometheus.yml /etc/prometheus/
My API is built with this Dockerfile
FROM mcr.microsoft.com/dotnet/sdk:6.0 AS build
ARG BUILDCONFIG=RELEASE
ARG VERSION=1.0.0
COPY ["myapi.csproj", "./src/myapi/"]
WORKDIR ./src/myapi/
RUN dotnet publish -c $BUILDCONFIG -o out /p:Version=$VERSION
FROM mcr.microsoft.com/dotnet/aspnet:6.0
WORKDIR /app
COPY --from=build /src/myapi/out ./
EXPOSE 5005/tcp
EXPOSE 50505/tcp
ENTRYPOINT ["dotnet", "myapi.dll", "--urls", "http://+:5005"]
In my Program.cs I have this:
...
app.UseMetricServer(50505, "/prometheus");
app.UseRouting();
app.UseHttpMetrics();
app.Run();
And if it matters, in the endpoint method I have this:
Counter _eventCounter = Metrics.CreateCounter("API_Events", "Entry Attempts", new string[] { "result" });
_eventCounter.WithLabels("test").Inc();
Host OS: Mac M2 Ventura 13.2.1
Docker: Docker version 20.10.22, build 3a2c30b