Can anyone help me to change port 8500 to 80 in Coldfusion ?
I don't remember why, but there's a reason CF defaults to port 8500. Might not be wise to change it. (I assume you're using the built-in webserver.)
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You can certainly move the tomcat port in CF by editing the port value in the internal webserver inside \cfusion\runtime\conf\server.xml (varies depending on version). You'll need to cycle the service for the change to take effect. It is probably better to stand up Nginx or Apache in front and proxy requests back to Tomcat. Apache or Nginx would listen on port 80 by default. If this is a production server you'll definitely want a web server proxying requests for security, stability, ... If it is development, no problem with using 8500 (or changing it as long as it doesn't conflict with another service already listening on the new port).
As suggested in above comment, if you are using built-in port than the port is 8500 which is a default port. If you are using ColdFusion 2016, it by default enables the built-in web server. If you want to run your app with port 80, you can either configure an external web server.