How to solve the problem that the docker listening port cannot be accessed

When using Docker to build an application environment, you are likely to encounter such a problem: an application is started in Docker, but it cannot be accessed through the specified port on the host.

This problem is actually caused by Docker's port binding mechanism. Applications in Docker containers are bound to the IP address of the container by default, and the host cannot be accessed through this IP address. Therefore, port mapping is required to map the ports in the container to the host so that applications on the host can access applications in the Docker container.

There are two common port mapping methods: static port mapping and dynamic port mapping.

Static port mapping refers to mapping a port in the Docker container to a specified port on the host, for example, mapping port 80 in the container to port 8080 on the host. This mapping method can be configured when Docker starts the container. For example:

$ docker run -p 8080:80 nginx

This command means to start an nginx container and map the container's port 80 to port 8080 on the host.

Dynamic port mapping means that Docker will automatically allocate an unoccupied host port and map the port in the container to the host port. This method can be achieved by using a colon (:), for example:

$ docker run -p 80 nginx

This command means to start an nginx container and map the container's port 80 to an unoccupied host port.

However, sometimes you will find that after using the above command, the host still cannot access the application in the Docker container. Why is this?

A common reason is that there is already an application occupying this port on the host. Docker will check whether the port is available. If it is occupied, it will fail to start. The solution to this problem is to modify the application configuration that occupies the port on the host, or map the port in the Docker container to other available ports on the host.

Another possible reason is that a firewall or other network security mechanism blocks communication between the host and the Docker container. If you are using a Linux system, you can check whether it is blocked by the firewall by viewing iptables rules. If it is blocked, you can modify the iptables rules to allow communication between the host and the Docker container.

In addition to the above two reasons, there are many other reasons that may cause the Docker listening port to be inaccessible, such as incorrect network configuration, Docker configuration error, etc. When encountering such a problem, you need to carefully analyze the situation and investigate the causes one by one.

In short, the problem of the Docker listening port being inaccessible requires comprehensive consideration and analysis of port mapping configuration, network security mechanism, firewall, etc. in order to quickly solve the problem.

The above is the detailed content of How to solve the problem that the docker listening port cannot be accessed. For more information, please follow other related articles on the PHP Chinese website!