Cups uses port 631 by default
Port 23
32239
By default it listens on SMTP port 25
Edit the ports.conf file and change the line listen 80 to listen 81 which is, all in all, remarkably straightforward.
port 25
Conventionally, an HTTP server listens on port 80. Regardless of the brand of web server that you are running, the server will typically listen for HTTP traffic on port 80 and HTTPS traffic on port 443.
TCP 3268
HTML itself doesn't use a port. You can transfer an HTML document over any port you'd like. The Hyper-text Transfer Protocol (HTTP) however, does have a standard, non-secure port: 80. Web servers listen by default at :80. If they're configured to listen for secure HTTPS connections, they will also listen on :443. Configuring the server to listen on a different port is often used to run two sites over the same domain name, and is pretty common on intranets.
port
You wouldn't use a shell script to do this. Any program could listen on a port by connecting or binding to a socket address. There are some utility languages such as Perl that could connect to a port and listen, but the listening would also be a function of what you are listening for.
No, physically they are different numbers. Logically, however, both port 80 and port 8080 listen for HTTP traffic, so logically they are the same. Port 80 is the standard, production port for HTTP traffic. Port 8080 is a 'test' port for HTTP traffic.
I think it means before assured of, or something along those lines.