How to check the port occupied by docker itself

Docker is currently one of the most popular containerized virtualization technologies. It can help developers and operation and maintenance personnel quickly deploy applications in different environments, and can better manage and isolate applications. However, Docker itself will also occupy some ports. This article will introduce how to check the ports occupied by Docker itself.

1. Docker ports

In Docker, each container can be assigned a different network port. These ports can be used to communicate with other applications on the host, and also Can be used to allow containers to communicate with each other. In Docker, each container has a unique IP address and can be easily accessed via port number. For example, if a container is assigned port 8080, the container can be accessed through http://localhost:8080.

In addition to these custom ports, Docker itself will also occupy some ports, which are used for container management and communication. So, how can we check the ports occupied by Docker?

2. Check the ports occupied by Docker

1. Use the Docker command line tool

You can use the Docker command line tool to check the ports of the currently running Docker container. The port used. Run the following command:

docker ps -a

This command will list all running containers, including the ports they use. As you can see, the ports occupied by Docker will be displayed in the "PORTS" column. For example, the following is a running container:

CONTAINER ID    IMAGE             COMMAND                  CREATED          STATUS          PORTS                  NAMES
04a1c0ca8b5c    nginx             "nginx -g 'daemon of…"   17 minutes ago   Up 17 minutes   0.0.0.0:80->80/tcp     nginx-container

This container uses port 80 as its default HTTP port, and this port has been mapped to port 80 of the host.

2. Using Docker internal commands

Another method is to use Docker internal commands to see which ports are being occupied by Docker. Run the following command:

docker port CONTAINER_NAME

where CONTAINER_NAME is the name of the running container. For example, if you want to list the ports used by a container named "nginx-container", you can run the following command:

docker port nginx-container

This command will list all ports used by the container. For example:

80/tcp -> 0.0.0.0:80

This means that Docker is using port 80 of the host machine to provide the Nginx server.

3. Summary

Docker is a very popular technology that can run applications in different environments through containerization technology. Docker itself will also occupy some ports, but you can easily see which ports are being occupied by using the Docker command line tool or Docker internal commands. Understanding this information can help you better manage and configure Docker containers and improve application stability and reliability.

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