Recently, one of my partners came with a request of changing his web application port. After digging around, I found an article that explained how to change Central Administration port number using stsadm.exe . I was sure that there should be a way to do it using GUI and guess what, there is a way to do it from Central Admin Site. It is quite simple.
1. Open Central Administation Site, go to Manage web application -> Choose the web application and in the ribbon Click on the arrow below Delete web application. Choose Remove SharePoint from IIS web site.
2. In the pop up box, make sure the right IIS site is chosen and click Yes and OK.
3.Make sure its also deleted from IIS.
4.In the Central Admin Site. click on the site again and now click on Extend in ribbon.
5. Fill in the details with the required port number and click OK.
Thats it!... now your web application is available on a new port number.