How to see http requests in fiddler going to docker container on windows?

Question

I'm using default docker on windows configuration and I run configure an application like this:

docker run -d -p 8080:80 --name openproject ...

I can access the application using browser, but in fiddler I can't see traffic to the docker container. I see other traffic, so I assume the browser has correct proxy settings.

I've set proxy in docker settings to fiddler (http://127.0.0.1:8888), but still nothing from the container is visible to fiddler.

'fiddler I can't see traffic to the docker container' -- What's the client application that sends traffic /into/ Docker? If it's a browser, what URL are you using? — EricLaw
Clients are a browser and powershell. Url is "localhost:8080" and "127.0.0.1:8080". Works in the browser and powershell, though fiddler does not see it. — mrówa
Powershell and .NET don't proxy requests to localhost/127.0.0.1, regardless of whether you specify a proxy. Requests from Chrome/Firefox absolutely should be shown. See groups.google.com/forum/#!topic/httpfiddler/SsZnGxdxklg — EricLaw
You misunderstand: .NET doesn't proxy requests whose URLs target 127.0.0.1 and localhost. (This isn't about the URL of the proxy, it's about the URL of the target resource). visualstudio.uservoice.com/forums/121579-visual-studio-ide/… — EricLaw
Alternatively, use localhost.fiddler as the address you use to call the Docker container. Fiddler will get that address and automatically turn it into localhost. — EricLaw

321_contact 321_contact · Accepted Answer · 2020-08-03T22:11:29

If you're trying to see traffic exiting the container, add this to your Dockerfile:

ENV http_proxy "http://host.docker.internal:8888/"
ENV https_proxy "http://host.docker.internal:8888/"

The http_proxy and https_proxy environment variables should be lowercase in a Linux container, contrary to what some of the Docker docs say (https://unix.stackexchange.com/questions/212894/whats-the-right-format-for-the-http-proxy-environment-variable-caps-or-no-ca)

host.docker.internal shortcuts you to the internal IP address used by the host (https://docs.docker.com/docker-for-windows/networking/).

Port 8888 is whatever port Fiddler is listening on in the host.

How to see http requests in fiddler going to docker container on windows?

2 Answers