Follow the below steps to update the defalt port 80 apache XAMP Apache server
1) Stop the XAMPP server, if it is running already.
2) Open the file httpd.conf(In my case its E:\xampp\apache\conf\httpd.conf)
Locate
Listen 80 ServerName localhost:80
And replace with the other port number(8012)
Listen 8012 ServerName localhost:8012
3) Open the file httpd-ssl(In my system its E:\xampp\apache\conf\extra\httpd-ssl.conf)
Locate the following lines
Listen 443 <VirtualHost _default_:443> ServerName localhost:433
Replace them by with a other port number(8013)
Listen 8013 <VirtualHost _default_:8013> ServerName localhost:8013
4) Restart the Apache server and http://localhost:8012/ should work.