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===== TCP vs HTTP =====

==== What is TCP? ====
**TCP (Transmission Control Protocol)** is a transport-layer protocol.
It provides a reliable, ordered byte-stream connection between two endpoints (client and server).

TCP is like a **pipe** that carries bytes.

==== What is HTTP? ====
**HTTP (Hypertext Transfer Protocol)** is an application-layer protocol.
It defines how to format requests and responses (methods like GET/POST, headers, body, status code).

HTTP runs **on top of TCP** (most commonly).

==== Key idea ====
  * TCP does NOT have “methods”.
  * HTTP has methods (GET/POST/PUT/DELETE), and those methods are just text/bytes sent through TCP.

So the correct mental model is:
  * **TCP = connection + byte stream**
  * **HTTP = rules for what bytes mean**

==== Diagram (layering) ====
  * Application layer: HTTP (request/response format)
  * Transport layer: TCP (reliable connection)
  * Network layer: IP (routing packets)

==== Example: Using TCP for HTTP (manual) ====
You can open a TCP connection and send an HTTP request manually:

<code go>
conn, _ := net.Dial("tcp", "example.com:80")
defer conn.Close()

fmt.Fprint(conn, "GET / HTTP/1.1\r\nHost: example.com\r\nConnection: close\r\n\r\n")
io.Copy(os.Stdout, conn)
</code>

==== Example: Using HTTP client (recommended) ====
Instead of crafting bytes yourself, use `http.Client`:

<code go>
resp, err := http.Get("http://example.com/")
if err != nil { return }
defer resp.Body.Close()
</code>

==== When to use which ====
  * Use **http.Client** when the server speaks HTTP/HTTPS (REST APIs, web, webhooks).
  * Use **net.Dial** when you need raw TCP for a non-HTTP protocol (Redis/MySQL/custom protocols).

==== Hard words (English) ====
  * **transport layer** /ˈtrænspɔːrt ˈleɪər/: tầng vận chuyển
  * **application layer** /ˌæplɪˈkeɪʃən ˈleɪər/: tầng ứng dụng
  * **protocol** /ˈproʊtəkɔːl/: giao thức
  * **byte stream** /baɪt striːm/: luồng byte
  * **reliable** /rɪˈlaɪəbəl/: đáng tin cậy
  * **ordered** /ˈɔːrdərd/: đúng thứ tự
  * **endpoint** /ˈendpɔɪnt/: điểm kết nối (client/server)
  * **craft** /kræft/: tự “chế”/tự tạo