I got requirement from client to change port number from 9704 to 80 for the Presentation Services .
Actual Url : http://localhost:9704/analytics
Required Url : http://localhost/analytics
To achieve the above requirement I followed the steps given below .
Note : First of all check for the available port numbers by running the commandnetstat -a from the command prompt .
Step1 : Login to weblogic console by using the below Url
Step2 : Click on servers from the left pane and Click on control –> Select bi_server1 –> Shutdown the server as shown in below screen shots .
Step3 : After shutdown , click on bi_server1 to change the Port number.
Step4: Click on Lock&Edit button as shown in below screenshot and observe that the default Listener Port is 9704 . Change this port number to 80 as shown in below screenshots .
Click on Save .
Step5: Click on Activate Changes to apply the changes .
Step6 : Go back to bi_server1 and start it .
Note : Here bi_server1 got started but I was not able to login into Presentation services (http://localhost:80/analytics) 
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Here I stopped all the OBIEE 11G services (Start –> All Programs–>Oracle Business Intelligence –> Stop BI Services) and start it again(Start –> All Programs–>Oracle Business Intelligence –> Start BI Services) .
Still All OBIEE Components were down .
To start all the BI Components ,I opened the command prompt and navigated to <OracleBIHome>/instances/instance1/bin (In my case D:\obieefmw\instances\instance1\bin) .
and started opmn services by running the batch file opmnctl.bat.
D:\obieefmw\instances\instance1\bin>opmnctl startall ;
Now all the services got up and running and can able to login to Presentation Services , http://localhost:80/analytics (OR) http://localhost/analytics
