Rails Server Fails to Bind to Port Due to Another Process. How to Terminate the Process Using the Port?

I am trying to start the web server for a Ruby on Rails application on Ubuntu 20.04 by running:
$ rails server
However, I get the following error:
=> Booting Puma
=> Rails 6.1.3.2 application starting in development
=> Run `bin/rails server --help` for more startup options
Puma starting in single mode...
* Puma version: 5.3.2 (ruby 2.7.4-p191) ("Birdie's Version")
* Min threads: 5
* Max threads: 5
* Environment: development
* PID: 12345
* Listening on http://127.0.0.1:3000
* Listening on http://[::1]:3000
=> Booted puma (Server is running on http://127.0.0.1:3000 and http://[::1]:3000)
Exiting
/usr/local/lib/ruby/gems/2.7.0/gems/puma-5.3.2/lib/puma/binder.rb:277:in `initialize': Address already in use - bind(2) for "127.0.0.1" port 3000 (Errno::EADDRINUSE)
I know I can run the Rails server on a different port, but how can I identify the processes that are blocking this port and terminate them?