The xterm application must be installed on both the RDC client and RDC server host.

The RDC server host must have a window manager installed. The RDC looks for icewm, fvwm, twm and mwm. You can override the window manager in use by providing the executable name of your window manager on the RDC's Advanced Options dialog.

Catalina (macOS 10.14) and newer users must install the free Real VNC viewer from https://www.realvnc.com/en/connect/download/viewer/macos/.