Actually, with the latest version of Symantec endpoint protection manger, it would automatically change the port 2638 to something else, if there is backup exec installed on the same server.
Also, by default, it will get installed on a custom HTTP port( 8014).
If, after installing you are not able to log into the Symantec Endpoint protection manager, then you would have to change the port 8443 to something else, like, 8444, or 8440.
To do this:
Go to C:/program files/Symantec/Symantec Endpoint protection manager/Tomcat/Conf, and open the file, server.XML with a notepad. Then Find " 8443", and replace it with 8440.
Save the file, and close it.
Then, go to start-Programs-Symantec Endpoint protection manager-Mgt.Server configuration wizard.
While running this, change port 8443 to 8440, and complete the wizard. Then you should be able to log into SEPM console, without any issues.