During the installation, the default ports 21200 and 21212 are used for communication between SAPinst, GUI server, and SAPinst GUI. SAPinst uses port 21200 to communicate with the GUI server. The GUI server uses port 21212 to communicate with SAPinst GUI. You get an error message if one of these ports is already in use by another service. In that case,
Execute sapinst.exe with the following command line parameter:
GUISERVER_DIALOG_PORT=21213"
For Example: sapinst.exe GUISERVER_DIALOG_PORT=21213