When I tried to start Apache server in XAMPP, an error message is shown:

9:40:41 AM [Apache] Attempting to start Apache app…
9:40:41 AM [Apache] Status change detected: running
9:40:42 AM [Apache] Status change detected: stopped
9:40:42 AM [Apache] Error: Apache shutdown unexpectedly.
9:40:42 AM [Apache] This may be due to a blocked port, missing dependencies,
9:40:42 AM [Apache] improper privileges, a crash, or a shutdown by another method.
9:40:42 AM [Apache] Press the Logs button to view error logs and check
9:40:42 AM [Apache] the Windows Event Viewer for more clues
9:40:42 AM [Apache] If you need more help, copy and post this
9:40:42 AM [Apache] entire log window on the forums
9:41:41 AM [Apache] Problem detected!
9:41:41 AM [Apache] Port 443 in use by “Unable to open process” with PID 4!
9:41:41 AM [Apache] Apache WILL NOT start without the configured ports free!
9:41:41 AM [Apache] You need to uninstall/disable/reconfigure the blocking application
9:41:41 AM [Apache] or reconfigure Apache and the Control Panel to listen on a different port

I changed the port in the httpd.conf file but it didn’t work. I rebooted the computer, but it didn’t

work either.

At last, I changed the port 443 to 553 in the httpd-ssl.conf file. It works.