Let’s talk about the solution to the problem that Docker cannot use port 80

Docker is an open source application container engine that can easily package applications into a container for deployment, running and management. However, when using Docker to deploy applications, sometimes you encounter the problem that port 80 cannot be used. This article will introduce some solutions to deal with this problem.

Problem Description

When using Docker to deploy an application, if the application needs to run on port 80, the following error message will usually appear:

Error starting userland proxy: listen tcp 0.0.0.0:80: bind: address already in use.

This error message indicates that there is already Another process is using port 80, so Docker cannot use this port.

Solution

The following introduces several methods to solve the problem that Docker cannot use port 80.

1. Stop the process occupying port 80

We can check the process occupying port 80 and stop the process so that Docker can use this port. The following are the steps to stop the process occupying port 80 on a Linux system:

1. Execute the following command to view the process ID occupying port 80:

   sudo lsof -i:80

2. View the process corresponding to the process ID:

   sudo ps -p [PID]

3. Stop the process:

   sudo kill [PID]

2. Modify the Docker mapped port

In addition to stopping the process occupying port 80, you can also avoid conflicts with the process occupying port 80 by modifying the Docker mapped port.

Assume that we have the application listening on port 8080 locally, and want to map port 80 of the Docker container to the local port 8080, then we can use the following command to start the Docker container:

sudo docker run -p 8080:80 [image name]

In this way, Docker maps the container's port 80 to the local port 8080, so that we can access the application in the browser.

3. Use Nginx proxy

Another way to solve the problem that Docker cannot use port 80 is to use Nginx proxy. We can configure Nginx to listen on port 80 and forward traffic to other ports in the Docker container. The following is a simple configuration example:

http {
    server {
        listen 80;
        server_name example.com;

        location / {
            proxy_pass http://localhost:8080;
            proxy_set_header Host $host;
            proxy_set_header X-Real-IP $remote_addr;
            proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
        }
    }
}

In this example, Nginx listens on port 80 and forwards traffic to the Docker container's port 8080.

Summary

The above are three methods to solve the problem that Docker cannot use port 80. You can choose the method that suits you according to your actual situation. When using Docker to deploy applications, you need to pay attention to port conflicts to avoid unnecessary trouble.

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