Possible usage includes (just a few examples):
Host interfacingFor reaching a session from the outside, host interfacing is the standard procedure for most virtialization products. Host interfacing acts like a bridge between the session and the outside world. The session it self must be configured with a static IP address (must be different from the host address) and on this address, the session can be reached from the outside by client applications.
Example. Host where VirtualBox is running has IP address 192.168.0.201 configured. A session of Ubuntu Server is running, with an active Apache web server on port 80. Host interfacing is configured, session has 192.168.0.202 as a static IP address. A browser points to the IP address of the session, thus: 192.168.0.202. This request reaches the session on port 80 and the Apache web server responds as usual.
Port forwardingWhen a session in configured with port forwarding, it is possible to reach the session from the outside by pointing to the host at a particular port. This port is then forwarded by VirtualBox to the session. The session then can respond. Essentially, the server where VirtualBox is running publishes a network service, but hides the implementation, i.e. the virtual machine.
Example. Host where VirtualBox is running has IP address 192.168.201 configured. A session of Ubuntu Server is running, with an active Apache web server on port 80. Port forwarding is configured from host port 8080 to guest port 80. A browser points to the IP address of the host, with the configured host port, thus: 192.168.0.201:8080. This request is forwarded by VirtualBox to the session on port 80 and the Apache web server responds. The browser does not know or has no means to detect that there's actually another (virtual) machine doing the work.
How fits VBoxTool in this?Port forwarding has huge benefits above host interfacing: far more flexible, no conflicts with other software, scalable, easy to configure, good portability of sessions, etc.
Although port forwarding configuration only requires just three commands, VBoxTool makes it even easier by automating this process. VBoxTool is capable for configuring port forwarding for all sessions, all at once in one command: 'vbox autostart'; configuration takes place in /etc/vbox/machines.conf. As many port pairs as wanted can be applied.
Example in /etc/vbox/machines.conf: "Ubuntu Server,3392,2022-22|80-80". In this example, the Ubuntu Server can be reached with SSH on the host IP address on port 2022. A web server is active within the session on port 80 and can be reached by pointing to the host IP address, on the normal web port, 80.
Note. Of course, a host port to be forwarded must be unique over all sessions over the host VirtualBox installation. Say several sessions have to be reached by SSH (internal port 22). Each session must have another host port, say session 1: 2022 and session 2: 3022, all pointing to the same internal session port for SSH, 22. By using VBoxTool, this is very easy to configure.