Docker log in to local registry with Docker Desktop for Mac

I'm working on developing a reverse proxy for docker registries, and I'm facing problems when trying to log in to the proxy application when running it locally. The application is listening on port 5000 for all the interfaces, and the thing is that I can successfully log in to the proxy when I run it through a docker container:

$> docker run -p 5000:5000 docker-proxy:latest

$> docker login -u admin -p password localhost:5000
Login Succeeded

However, when I run the application directly on my local without using a container, I get a connection refused error:

docker login -u admin -p password localhost:5000
Error response from daemon: Get "http://localhost:5000/v2/": dial tcp [::1]:5000: connect: connection refused

My computer is a Mac running macOS Moterey (v12.6) and the application is configured to listen on address [::] (it also works listening on the IPv4 equivalent 0.0.0.0) and port 5000.

Could someone explain to me the reason for this?

It seems that I've finally found the root cause of this issue. As you can learn from this post, Docker for desktop creates a Linux virtual machine in Mac and Windows, and the docker engine and most of the docker tools actually run on that VM instead of on the host operating system. That said, the issue I was facing is that when I run docker login ... localhost, that localhost actually points to the VM instead of the host OS, so there's no docker registry running and listening there. To be able to connect to the application running on my host OS I had to provide docker login with an address where it can find the running registry, for example, the IP address of the network interface I use to connect to my LAN (192.168.0.6 in my case, you can take yours using some tool like ifconfig).

Once I had the address, I faced a different issue. When to docker login to it, I got an error saying that server gave an HTTP response to HTTPS client. That was because my proxy was handling requests through HTTP instead of HTTPS protocol (the common thing when you are developing an application I guess).

$> docker login -u admin -p password 192.168.0.26:5000
Error response from daemon: Get "https://192.168.0.26:5000/v2/": http: server gave HTTP response to HTTPS client

To fix that, I configured my proxy to run through HTTPS using some self-signed certs, but then it yelled about the certificates not being valid for the requested address.

docker login -u admin -p password 192.168.0.26:5000
Error response from daemon: Get "https://192.168.0.26:5000/v2/": x509: certificate is valid for 127.0.0.1, not 192.168.0.26

Finally, to fix the last issue I had to configure the proxy application as an insecure registry in my docker engine config. To do this you
have to follow the instructions from this official Docker guide. In case you are a Mac
user, you will find the config file in ~/.docker/daemon.json, and you will have to add the following entry and restart the Docker daemon for it to take effect:

{
  "insecure-registries" : ["http://192.168.0.26:5000"]
}

Or even easier, you can do it all from the settings section of the Docker Dashboard in Docker Desktop, going to the Docker Engine section,
editing the config, and clicking on the Apply & restart button.

Then, I was finally able to successfully run the docker login command:

$> docker login -u admin -p password 192.168.0.26
Login Succeeded