Exploring Network Connections
Computers connect to other computers using an IP address and a port. Ports allow multiple network connections from a single machine. Imagine that the IP address is the street address to an apartment complex, and each port is an apartment number in the building.
For example, when you make a request to google.com with your web browser, your browser uses port 80, the default port for web traffic. To complete that request, your browser needs to figure out which IP address google.com resolved to, so it makes a request to a DNS server using port 53, the default port for DNS queries.
When you installed the openssh-server package, your Ubuntu machine started listening for incoming connections on port 22. When you connected ...
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