Networking and Communication
How a request gets from a phone to a server and back: DNS, TCP and UDP, HTTP and HTTPS, API styles, and keeping connections open for real-time updates.
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Module 03
Networking and Communication
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3.1
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What Happens When You Open a Web Page
Follow one request from typing a URL to seeing the page: DNS lookup, TCP and TLS handshakes, the load balancer, the app server, the database and back. Every later topic zooms into one of these steps.
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3.2
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DNS: The Internet’s Phone Book
How the Domain Name System turns names like example.com into IP addresses, why answers are cached with a TTL, the record types you will meet, and how DNS is used for load balancing and fail-over.
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3.3
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HTTP and HTTPS
The protocol behind every web page and API: methods and status codes, safe and idempotent requests, caching headers, how HTTPS keeps traffic private, and what HTTP/2 and HTTP/3 changed.
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3.4
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TCP vs UDP
TCP gives you a reliable, ordered stream at the cost of handshakes and waiting for lost packets; UDP sends independent packets with no guarantees and no delay. Learn how each works and when to choose which.
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3.5
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API Styles: REST, RPC and gRPC, GraphQL
How services expose their functions: REST around resources, RPC and gRPC around actions with strict contracts, and GraphQL letting clients ask for exactly the fields they need. Plus pagination and versioning that keep APIs usable as they grow.
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3.6
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Real-Time: Polling, Long Polling, WebSockets and SSE
Four ways for a server to tell a client that something happened: polling, long polling, Server-Sent Events and WebSockets. How each works, what it costs, and how to scale millions of open connections.