When you connect to a web server (such as
https://coderanch.com/) and you do not specify a particular port to use, then you must be using the default port. You can read a basic primer on HTTP in
wikipedia's Hypertext Transfer Protocol article, which will tell you the default port, and it will also give you a list of relevant RFCs that will give you a much greater understanding of what is going on.
Alternatively you could look up HTTP in wikipedia's
list of TCP and UDP port numbers - this will also give you the default port number.
