How do computers connect to each other over the Internet?

Computers Do Not connect directly to each other via the internet, the internet service connects computers to each other, for example Skype Connects two computers with each other through VoIP protocol that opens a port on both computers to send and receive information, Websites use an internet protocol known as HTTP to connect a computer to a website hosting server,

so based on my humble knowledge i don't think computers connect directly to each other over the internet unless through a service installed on both computers.