When you have (or planning to have) more than one SAP instance on the same server, it may happen that you will need to run SAPinst at the same time as somebody else.
If you attempt to run it on default port it will not start, the solution is to specify different ports for SAPINST_DIALOG_PORT and GUISERVER_DIALOG_PORT i.e.
./sapinst SAPINST_DIALOG_PORT=21214 GUISERVER_DIALOG_PORT=21215
