Solution

You can choose to use the host.docker.internal hostname, which is a specially created hostname that the Docker service has automatically created.

This unique hostname resolves to the operating system of the host, which may be Windows, Linux, or Mac. 

Testing

To test our above-mentioned process, we will run two tests of our theory:

• Test 2 is necessary because the first test cannot definitively confirm that the machine being tested is the host machine, even if it does respond to pings.

• Connect to an active service on the host machine (mine was a MAC) to confirm that our host operating system is running there.

Test to analyze whether Ping works

First, we will start with the easy test to analyze our theory:

                                               Source:> >Unbiased Coder

We can observe from the test above that we received the response right away. Additionally, you can see that the host operating system has been assigned the IP address 192.168.65.2 by docker internally. 

Note: Another thing to consider is that the host system might not be responding to a PING. The firewall rule within the Docker container may be the cause of this. Try utilizing the previously discussed shell connection method in this situation. Using the command below, will establish a connection to the instance plus and flush the firewall rules:

After that, execute the ping command once more without stopping your Docker container. Should it be successful, your connection from a Docker container to localhost will be blocked by a firewall. Lastly, remember that since we previously flushed all of the firewall rules, you should either restart the Docker instance or, if you neglected to do so, restore your firewall rules.

Test whether we can connect to a service in the host machine

To see if it produces any results, we will attempt to connect to a few test services in our host operating system. We will use> >Isof, a tool that helps you identify open file descriptors inside a Unix-based OS. 

Since Mac is based on Unix, it will function flawlessly. Above all, we need an open port, so in this instance, we're using file descriptors with open IPv4 ports. You can use the command listed below:

                                                        Source:> >Unbiased Coder

Moving forward, let’s see if the command is working properly:

                                         Source:> >Unbiased Coder

Return to the Docker container to verify that it has established a successful connection to our native host system's MAC services' open port. Take note that the netcat command is being used to test connectivity in this case. This facilitates the execution of a specific TCP/IP connection to the port that the command line specifies. 

Additionally, you have the option to uniquely identify your Docker instances, including specific usernames, in the build process or docker files. 

Here's an example to help you better understand it:

                                                     Source:> >Unbiased Coder

The example above illustrates how we specified the hostname myubuntu. To verify this, we start the Docker container and establish a connection with it. The item appears in the host file and hostname, and MyUbuntu is now the default prompt.

This tip will help you identify and ping your Docker containers without any problems when they are out of context, and it will also let you know what to expect from them in advance.