7 Remote virtual machines 7.1 Remote display (VRDP support) VirtualBox can display virtual machines remotely, meaning that a virtual machine can execute on one machine even though the machine will be displayed on a second computer, and the machine will be controlled from there as well, as if the virtual machine was running on that second computer. For maximum flexibility, starting with VirtualBox 4.0, VirtualBox implements remote machine display through a generic extension interface, the VirtualBox Remote Desktop Extension (VRDE). The base open-source VirtualBox package only provides this interface, while implementations can be supplied by third parties with VirtualBox extension packages, which must be installed separately from the base package. See chapter 1.5, Installing VirtualBox and extension packs, page 14 for more information. Oracle provides support for the VirtualBox Remote Display Protocol (VRDP) in such a VirtualBox extension package. When this package is installed, VirtualBox versions 4.0 and later support VRDP the same way as binary (non-open-source) versions of VirtualBox before 4.0 did. VRDP is a backwards-compatible extension to Microsoft’s Remote Desktop Protocol (RDP). Typically graphics updates and audio are sent from the remote machine to the client, while keyboard and mouse events are sent back. As a result, you can use any standard RDP client to control the remote VM. Even when the extension is installed, the VRDP server is disabled by default. It can easily be enabled on a per-VM basis either in the VirtualBox Manager in the “Display” settings (see chapter 3.5, Display settings, page 45) or with VBoxManage: VBoxManage modifyvm "VM name" --vrde on If you use VBoxHeadless (described further below), VRDP support will be automatically en- abled since VBoxHeadless has no other means of output. 7.1.1 Common third-party RDP viewers Since VRDP is backwards-compatible to RDP, you can use any standard RDP viewer to connect to such a remote virtual machine (examples follow below). For this to work, you must specify the IP address of your host system (not of the virtual machine!) as the server address to connect to, as well as the port number that the RDP server is using. By default, VRDP uses TCP port 3389. You will need to change the default port if you run more than one VRDP server, since the port can only be used by one server at a time you might also need to change it on Windows hosts since the default port might already be used by the RDP server that is built into Windows itself. Ports 5000 through 5050 are typically not used and might be a good choice. The port can be changed either in the “Display” settings of the graphical user interface or with --vrdeport option of the VBoxManage modifyvm command. You can specify a comma- separated list of ports or ranges of ports. Use a dash between two port numbers to specify a range. The VRDP server will bind to one of available ports from the specified list. For example, VBoxManage modifyvm "VM name" --vrdeport 5000,5010-5012 will configure the server to bind to one of the ports 5000, 5010, 5011 or 5012. See chapter 8.7, VBoxManage modifyvm, page 109 for details. 90