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).
If you need to run a web-server on a TCP/IP port other than 80, the visitor will need to specify this port directly in the URL (see above), or you need to point the DNS A-record to the IP address of a different web-server (running on port 80) which redirects your domain name to your own server IP address and port number.
For details, please see the reference articles below.
For more information, please see the following knowledge base articles: