How to keep Visual Studio or Docker from changing the host port numbers?

I have dockerized my web application and can run it within Visual Studio, however, the host port number it chooses to use is not consistent.

Where do I configure it to always use the same port numbers?

I found I can do this by editing launchSettings.json and specifying the values there. This is similar to Arjun's answer, but as far as I can tell there's no UI to add the port numbers like when selecting IIS Express - so you have to edit the file directly.

Update: Actually, in my case, I still had problems getting the port numbers to be consistent after doing this. What worked for me was right-clicking on the project and adding "Container Orchestration Support". Then set the port numbers in the docker-compose project. This helped with overriding environment variables as well.

Update 2: For anyone changing the port numbers in launchSettings.json, you may also need to delete any existing containers and/or images for the changes to take effect. Cleaning the solution wasn't sufficient for me. I had to delete them from Docker Desktop.

In your projects launchSettings.json add the following items (in yellow):

I set the port in docker-compose.yml, but it didn't work.
Turns out it was overriden by docker-compose.override.yml.

You can either:

• set the ports inside override (applies always)
• change it in docker-compose.yml and remove it from override (you can then set different ports for different configurations)

There is no UI but you can modify the .csproj project file to add DockerfileRunArguments

<PropertyGroup>	
 <DockerLaunchAction>LaunchBrowser</DockerLaunchAction>
 <DockerLaunchUrl>http://{ServiceIPAddress}</DockerLaunchUrl>
 <DockerfileRunArguments>-p 8080:80</DockerfileRunArguments>
</PropertyGroup>

Edit:

If you are using NetCore then you can go with the launchSettings.json solution. For the framework, you can either use "Container Orchestration Support" or this hack.

After adding docker-compose orchestration support from within VS2019 I had the same issue. I fixed it by changing

    ports:
      - "80"
      - "443"

to

    ports:
      - "80:80"
      - "443:443"

According to the docker-compose documentation, ports are configured in the following way: -

> Either specify both ports (HOST:CONTAINER), or just the container port (an ephemeral host port is chosen).

So since the host ports aren't defined in the default VS2019 docker-compose file, These are chosen ephemerally. I had to look up the definition of this word which appears to be a synonym of transient.

> lasting for a very short time.

I tried setting "httpPort": 8080 in launchSettings.json, but it didn't work at all, even after removing and recreating the container.

What worked for me was:

Right click project in Visual Studio > Add > Container Orchestration Support (if you've set this up already, you don't need to do it again)

This sets up a docker-compose.yml file, with a Dockerfile for the app. There's also a docker-compose.override.yml file that's used for overriding the docker-compose.yml with environment-specific settings (e.g. for dev, or prod). By default, this exposes the container port as port 80, but doesn't expose a fixed host port to map the container port ot. To change it (e.g. to map a fixed host port of 8080):

version: '3.4'

services:
  coreapp:
    environment:
      - ASPNETCORE_ENVIRONMENT=Development
    ports:
      - "8080:80"

Note the use of double quotes i.e. "8080:80"

For me, I was able to find it with the following steps in Visual Studio 2017:

1. Right click on the web project, then click Properties.
2. Click on the Debug tab.
3. Under the Profile IIS Express, you will find the port at the App URL box.

For more, visit: Docker Port Managing

I had the same issue and had to modify docker-compose.override.yml in the docker-compose project.

Originally, the ports section looked like that (which was causing automatic port assignments):

ports:
  - "80"
  - "443"

I changed it to

ports:
  - "8080:80"
  - "56850:443"

And that forced the Debug to use the ports specified.