Programming
A searchable guide to practical network terms used in local development, browser requests, APIs, Docker, and deployment troubleshooting.
42 matching terms
Addresses and names
IP address
192.168.1.25A numeric address used to find a device on a network.
Use it when another device needs to reach your computer, server, or container host.
192.168.1.25Explain which IP address I should use from another device.
Addresses and names
IPv4
192.168.0.10The common four-part IP address format.
Most local network examples use IPv4 addresses such as 192.168.x.x or 10.x.x.x.
192.168.0.10Tell me whether this address is an IPv4 local network address.
Addresses and names
IPv6
::1A newer, longer IP address format designed to provide many more addresses.
You may see IPv6 in logs, localhost bindings, or server network output.
::1Explain whether this log is using IPv4 or IPv6.
Addresses and names
localhost
http://localhost:3000A name that means the same machine where the code or browser is running.
Use it from the same computer that runs the development server.
On a phone, localhost means the phone itself, not your development computer.
http://localhost:3000Explain why localhost works on my computer but not on my phone.
Addresses and names
127.0.0.1
http://127.0.0.1:3000The common IPv4 loopback address for the current machine.
Use it as a numeric alternative to localhost.
http://127.0.0.1:3000Explain whether localhost and 127.0.0.1 are equivalent here.
Addresses and names
0.0.0.0
next dev -H 0.0.0.0An address used by servers to listen on all available network interfaces.
Use it when another device on the same network needs to reach your dev server.
It can expose a development server more broadly than localhost.
next dev -H 0.0.0.0Explain whether this dev server should bind to 0.0.0.0.
Addresses and names
Hostname
my-laptop.localA readable name for a device or server.
Use it when a network name is easier to remember than an IP address.
my-laptop.localExplain whether this hostname resolves to the expected IP.
Addresses and names
Domain
example.comA human-readable internet name for a website or service.
Use domains for public sites instead of asking users to remember server IP addresses.
example.comExplain what domain this deployed site should use.
Addresses and names
DNS
example.com -> 93.184.216.34The system that translates domain names into IP addresses.
Use DNS records when connecting a domain to a hosting service or server.
example.com -> 93.184.216.34Explain which DNS record is needed for this domain.
Ports and connections
Port
3000A number that identifies which app or service receives traffic on a machine.
Development servers often use ports such as 3000, 3001, 5173, or 8000.
3000Tell me which port this server is using.
Ports and connections
Listen
Ready on http://localhost:3000A server is listening when it is ready to accept requests on an address and port.
Check listening output to know which URL can be opened in the browser.
Ready on http://localhost:3000Explain where this server is listening.
Ports and connections
Port forwarding
8080 -> 3000Forwarding traffic from one port or machine to another port or machine.
Use it in routers, tunnels, containers, and remote development environments.
8080 -> 3000Explain where this port is forwarded.
Ports and connections
Firewall
Allow incoming connections on port 3000A rule system that allows or blocks network traffic.
Check it when a server runs locally but another device cannot connect.
Allow incoming connections on port 3000Explain whether a firewall could block this local connection.
Web requests
URL
https://example.com/docs?page=1The full address used to request a web resource.
A URL includes protocol, host, optional port, path, query string, and sometimes a fragment.
https://example.com/docs?page=1Break this URL into protocol, host, port, path, and query.
Web requests
Path
/ko/reference/dockerThe part of a URL that identifies a route or resource on the server.
Use it to understand which page or API endpoint is being requested.
/ko/reference/dockerTell me which app route this URL path maps to.
Web requests
Query string
?page=1&lang=koThe part of a URL after ? that passes extra parameters.
Use it for filters, page numbers, search terms, and lightweight options.
?page=1&lang=koExplain what query parameters this URL sends.
Web requests
HTTP
http://localhost:3000The basic protocol browsers and servers use for web requests and responses.
Local development often uses HTTP before production HTTPS is configured.
http://localhost:3000Explain whether this local URL uses HTTP or HTTPS.
Web requests
HTTPS
https://example.comHTTP protected by TLS encryption.
Use HTTPS for public sites, login, cookies, payments, APIs, and production traffic.
https://example.comExplain whether this deployed site needs HTTPS.
Web requests
HTTP method
GET /api/toolsA verb that tells the server what kind of action the request wants.
GET usually reads data, while POST usually creates or submits data.
GET /api/toolsExplain which HTTP method this API request should use.
Web requests
Status code
200 OK / 404 Not Found / 500 Internal Server ErrorA number that summarizes the result of an HTTP response.
Use it to quickly separate success, redirect, client error, and server error responses.
200 OK / 404 Not Found / 500 Internal Server ErrorExplain what this HTTP status code means.
Web requests
Header
Content-Type: application/jsonMetadata sent with an HTTP request or response.
Headers carry content type, authorization, cookies, cache rules, and CORS settings.
Content-Type: application/jsonExplain the important headers in this response.
Web requests
Body
{"name":"demo"}The main data content sent in an HTTP request or response.
POST and PUT requests often send JSON data in the body.
{"name":"demo"}Explain what data this request body sends.
Browser security
Origin
http://192.168.1.25:3000The combination of protocol, host, and port.
Use origin to reason about CORS, cookies, and browser security rules.
Changing only the port creates a different origin.
http://192.168.1.25:3000Identify the origin of this URL.
Browser security
Same-origin policy
https://app.example.com cannot freely read https://api.example.comA browser rule that restricts how pages can read data from other origins.
Use it to understand why browser API requests can fail even when the server is reachable.
https://app.example.com cannot freely read https://api.example.comExplain whether this is a same-origin policy problem.
Browser security
CORS
Access-Control-Allow-Origin: https://app.example.comA server-side permission system that lets browsers use responses from another origin.
Use it when a frontend app calls an API hosted on a different origin.
CORS must be allowed by the server that sends the response.
Access-Control-Allow-Origin: https://app.example.comTell me whether this CORS error should be fixed in frontend code or server settings.
Browser security
Cookie
Set-Cookie: session=abc; HttpOnlySmall data stored by the browser and sent back to matching sites.
Cookies are often used for sessions, preferences, and authentication state.
Set-Cookie: session=abc; HttpOnlyExplain whether this login state is stored in a cookie.
Browser security
Session
session_id=abc123A way to remember user state across multiple requests.
Use sessions to maintain login state or temporary server-side user data.
session_id=abc123Explain how this app keeps the user session.
Browser security
Token
Authorization: Bearer <token>A string used to prove identity or permission.
Use tokens for API authentication, temporary access, and service-to-service requests.
Tokens can grant access, so they should not be exposed in public code or logs.
Authorization: Bearer <token>Check whether this token is being exposed to the browser.
Browser security
TLS certificate
Let's Encrypt certificateA certificate used by HTTPS to prove a site's identity and encrypt traffic.
Use it when serving a production site over HTTPS.
Let's Encrypt certificateExplain why this browser says the certificate is invalid.
Local development
Local network
Laptop and phone on the same Wi-FiA private network where nearby devices can communicate, such as the same Wi-Fi.
Use it when testing a local dev server from a phone or tablet.
Laptop and phone on the same Wi-FiExplain whether these devices are on the same local network.
Local development
LAN IP
192.168.1.25An IP address used inside a local network.
Use it from another device on the same network to reach your development machine.
192.168.1.25Tell me the difference between localhost and a LAN IP.
Local development
Network URL
http://192.168.1.25:3000A URL that another device on the same network can use to reach a local server.
Use it when testing a responsive page on a phone or tablet.
The dev server may also need to listen on 0.0.0.0 and allow the origin.
http://192.168.1.25:3000Explain how to open this dev server from a phone.
Local development
Dev server
npm run devA local server used while developing and testing an app.
Use it for fast reloads, local previews, and debugging before production build.
npm run devExplain which local URL and network URL this dev server exposes.
Local development
HMR
/_next/webpack-hmrA development feature that updates the browser when code changes.
Use it to keep the browser state while editing UI code.
/_next/webpack-hmrExplain whether this blocked request is related to HMR.
Server and Docker
Proxy
Browser -> proxy -> APIA server that sends requests on behalf of a client.
Use it to route requests, hide backend details, or avoid direct browser-to-API calls in development.
Browser -> proxy -> APIExplain whether this API request goes through a proxy.
Server and Docker
Reverse proxy
Nginx -> app:3000A server that receives public traffic and forwards it to internal services.
Use it for HTTPS termination, routing, compression, caching, and forwarding to app servers.
Nginx -> app:3000Explain how this reverse proxy routes traffic to the app.
Server and Docker
Docker port mapping
3000:3000A mapping from a host port to a container port.
Use it so a browser on the host can reach a web app running inside a container.
In Docker ports, the left side is the host port and the right side is the container port.
3000:3000Explain the browser URL for this Docker port mapping.
Server and Docker
host.docker.internal
http://host.docker.internal:3000A special hostname containers can use to reach the host machine in many Docker Desktop setups.
Use it when a container must call a service running on the host machine.
http://host.docker.internal:3000Explain whether this container should use host.docker.internal.
Server and Docker
Service name
postgres://db:5432/appIn Docker Compose, services can often reach each other by service name.
Use db, api, redis, or other compose service names instead of localhost between containers.
postgres://db:5432/appExplain why this container should use the db service name instead of localhost.
Server and Docker
Load balancer
Client -> load balancer -> app serversA system that distributes incoming traffic across multiple servers.
Use it when one app has multiple running instances for scale or reliability.
Client -> load balancer -> app serversExplain where a load balancer fits in this deployment.
Server and Docker
CDN
Static assets served from an edge cacheA distributed network that serves content from locations closer to users.
Use it to speed up static assets, images, scripts, styles, and cached pages.
Static assets served from an edge cacheExplain whether this static site benefits from a CDN.
Server and Docker
Cache
Cache-Control: max-age=3600Saved data or responses reused to make future requests faster.
Use cache for static files, API responses, pages, and CDN edge content.
Old cached content can make a fixed bug appear unfixed.
Cache-Control: max-age=3600Explain whether this issue could be caused by cache.