Attempts to assign a different port number from IBM Rational Performance Tester (RPT) is not possible as the 'Server 'option is missing from the preferences Wizard.
Open IBM Rational Performance Tester (RPT) and click Windows Menu > Preferences >Test
The Server option is missing from the list
RPT 8.3 started using JRE7 as compared to JRE6 as in previous versions.
Changing the default JRE 7 pointed from eclipse.ini file leads to adverse effects.
Resolving the problem
Ensure the JRE pointed from eclipse.ini file pointed from C:\Program Files (x86)\IBM\SDP
Default is C:\Program Files (x86)\IBM\SDP\jdk\jre\bin\javaw.exe which is JRE7