An IP address identifies a machine on a network. A port identifies a service on that machine. Web traffic usually uses TCP: 80 for HTTP and 443 for HTTPS.
https://example.com -> example.com:443
TCP gives reliable ordered delivery. UDP is lighter and used where latency matters more than perfect delivery, such as DNS and real-time media.
TIP
If an app is down, ask three questions: is DNS correct, is the port open, and is a process listening?
Further Learning
“TCP vs UDP web developers” — protocol tradeoffs
“ss listening ports Linux” — inspect services
“common TCP ports HTTP HTTPS SSH” — port basics
IP, Ports, TCP, and UDP
Computers on a network find each other the same way you find a friend: with an address, and then the right apartment number. On the internet, the IP address is the building, and the port is the apartment (which specific service on that machine).
IP + port
IP address — identifies a machine (like 142.250.80.46).
Port — identifies a service on that machine.
When you visit https://example.com, you’re really connecting to that server on port 443 (the standard port for secure web traffic). Plain (non-secure) web uses port 80.
https://example.com → example.com:443
TCP vs UDP: two ways to send data
TCP is like a phone call with confirmation — it guarantees everything arrives, in order, nothing lost. Web pages use TCP.
UDP is like shouting across a room — faster, but no guarantee everything arrives. Good for things where speed beats perfection, like live video or games.
For almost all web work, you’re using TCP without thinking about it.
TIP
When an app is down, check three things in order: is the address (DNS) right, is the port open, and is a program actually listening on it?
In one sentence
An IP address points to a machine and a port points to a service on it (web = 443 for HTTPS, 80 for HTTP) — and web traffic rides on TCP, which reliably delivers everything in order.
Want to go deeper?
Switch to Expert mode above for the TCP/UDP trade-offs in detail and tools for inspecting listening ports.