How to find Port number of IP address?

Question

We can find out IP address of a domain name or URL. But how to find out Port number on which a domain name is hosted?

Answer 1

Unfortunately the standard DNS A-record (domain name to IP address) used by web-browsers to locate web-servers does not include a port number. Web-browsers use the URL protocol prefix (http://) to determine the port number (http = 80, https = 443, ftp = 21, etc.) unless the port number is specifically typed in the URL (for example "http://www.simpledns.com:5000" = port 5000).

Can I specify a TCP/IP port number for my web-server in DNS? (Other than the standard port 80)