WEBVTT

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What does the number after localhost mean in a preview address?

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A port helps direct a connection to the appropriate service on a device.

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Read the host and port together.
6 port basics.

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The host identifies the destination
A hostname or IP address identifies where the connection is going.
Hostname · IP address · Destination device

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The port identifies a service
Different network services can listen on different ports.
Service port · Listening application · Intended connection

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A URL can show the port
It appears after the host, separated by a colon.
Host name · Colon separator · Port number

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Web schemes have default ports
HTTP commonly uses 80; HTTPS commonly uses 443.
HTTP 80 · HTTPS 443 · Scheme defaults

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Local previews often use others
A development server can listen on its configured local port.
Preview application · Configured port · Running service

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Check the exact preview address
A wrong port can reach another service or fail to connect.
Correct host · Correct port · Expected application

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Your checklist
The host identifies the destination · The port identifies a service · A URL can show the port · Web schemes have default ports · Local previews often use others · Check the exact preview address

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Use the port supplied for the intended service.
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