How to setup a Ubuntu VirtualBox for remote telnet access

An Ubuntu 19.05 VirtualBox instance running on a Windows machine can be configured to be accessible remotely via telnet.

This can be simply by configuring the Ubuntu VirtualBox instance's network port forwarding in the VirtualBox graphical user interface. The following points illustrate the procedure.

Configure Oracle VirtualBox

1. Start Oracle VirtualBox.
   
   
2. Select the Ubuntu instance e.g. Ubuntu19. Click the Settings icon.
3. In the Settings dialog box, select Network.
   
   
4. Click the buton Port forwarding.
   
   The Port Forwarding Rules dialog box appears.
   
5. Click the Add icon.
   
   
6. Change the Host Port to an unused port e.g. 3023. Change the Guest Port to 23.
   
   Note: in this example, when accessing remotely, the port called should be 3023.
7. Click OK to all the boxes.

Now run up the Ubuntu instance. If the telnet server is not installed, the open up a Terminal and run the following command.

$ sudo apt install telnetd

Then either restart the service or simply reboot.

On a remote computer, type in the following command to access the Ubuntu instance.

$ telnet 192.???.???.??? 3023

Note: replace 192.???.???.??? with the IP address of the Windows host

Note: If all the parameters are correct, the telnet response should be displayed as shown below.