Batch 5: Protocols & Security Networking Apache & NGINX Docker ← Full TOC

🌐 HTTP & HTTPS — HTTP methods, status codes, headers, HTTPS, TLS handshake

HTTP (HyperText Transfer Protocol) is the foundation of data communication on the web. HTTP/1.1 is text-based, HTTP/2 adds multiplexing, HTTP/3 uses QUIC. HTTPS is HTTP over TLS — always use HTTPS in production.

📋 Reference

Item	Syntax / Value	Description
GET	GET /path HTTP/1.1	Retrieve resource — safe, idempotent, cacheable
POST	POST /path HTTP/1.1	Submit data — creates resource, not idempotent
PUT	PUT /path HTTP/1.1	Replace entire resource — idempotent
PATCH	PATCH /path HTTP/1.1	Partial update — idempotent
DELETE	DELETE /path HTTP/1.1	Remove resource — idempotent
HEAD	HEAD /path HTTP/1.1	Like GET but no body — check existence/headers
OPTIONS	OPTIONS /path HTTP/1.1	List supported methods — used in CORS preflight
200 OK	200 OK	Request succeeded
201 Created	201 Created	Resource created (POST/PUT)
204 No Content	204 No Content	Success, no body (DELETE)
301 Moved Permanently	301 Moved Permanently	Permanent redirect — update bookmarks
302 Found	302 Found	Temporary redirect
304 Not Modified	304 Not Modified	Cached version is current — use it
400 Bad Request	400 Bad Request	Malformed request syntax
401 Unauthorized	401 Unauthorized	Authentication required
403 Forbidden	403 Forbidden	Authenticated but not authorized
404 Not Found	404 Not Found	Resource does not exist
405 Method Not Allowed	405 Method Not Allowed	HTTP method not supported
409 Conflict	409 Conflict	State conflict — duplicate, version mismatch
422 Unprocessable	422 Unprocessable Entity	Validation error on submitted data
429 Too Many Requests	429 Too Many Requests	Rate limit exceeded
500 Internal Server Error	500 Internal Server Error	Server-side error
502 Bad Gateway	502 Bad Gateway	Upstream server returned invalid response
503 Service Unavailable	503 Service Unavailable	Server overloaded or down for maintenance
Content-Type	Content-Type: application/json	MIME type of request/response body
Authorization	Authorization: Bearer token123	Auth token in request header
Cache-Control	Cache-Control: max-age=3600, public	Caching directive
CORS	Access-Control-Allow-Origin: *	Cross-Origin Resource Sharing header
HTTP/2	Multiplexed streams, header compression, server push	Multiple requests over one TCP connection
HTTP/3	QUIC protocol — UDP-based, 0-RTT connection	Faster than HTTP/2, especially on lossy networks

💡 Example

# HTTP with curl — the universal HTTP client

# ── Basic requests ────────────────────────────────────────────
curl https://jsonplaceholder.typicode.com/posts/1
curl -s https://api.example.com/users | python3 -m json.tool

# Verbose — show full request and response headers
curl -v https://www.mywebuniversity.com/

# HEAD request — check headers without body
curl -I https://www.mywebuniversity.com/

# ── Methods ───────────────────────────────────────────────────
# GET with query params
curl "https://api.example.com/courses?subject=python&limit=10"

# POST JSON
curl -X POST https://api.example.com/courses \
  -H "Content-Type: application/json" \
  -H "Authorization: Bearer mytoken123" \
  -d '{"title":"Python 3 Advanced","credits":3,"level":"advanced"}'

# PUT (full replace)
curl -X PUT https://api.example.com/courses/42 \
  -H "Content-Type: application/json" \
  -d '{"title":"Updated Title","credits":4}'

# PATCH (partial update)
curl -X PATCH https://api.example.com/courses/42 \
  -H "Content-Type: application/json" \
  -d '{"credits":4}'

# DELETE
curl -X DELETE https://api.example.com/courses/42 \
  -H "Authorization: Bearer mytoken123"

# ── Python HTTP client ────────────────────────────────────────
import urllib.request, json

# GET
with urllib.request.urlopen('https://jsonplaceholder.typicode.com/posts/1') as r:
    data = json.loads(r.read())
    print(f"Title: {data['title']}")

# POST with requests library (pip install requests)
import requests

resp = requests.post('https://jsonplaceholder.typicode.com/posts',
    headers={'Content-Type': 'application/json'},
    json={'title': 'MyWebUniversity', 'body': 'Free education', 'userId': 1})
print(f"Status: {resp.status_code}")
print(f"Created: {resp.json()}")

# Session with auth (reuse connection + headers)
session = requests.Session()
session.headers.update({'Authorization': 'Bearer mytoken', 'Accept': 'application/json'})

r = session.get('https://api.example.com/courses')
print(r.json())

# ── HTTP status codes in Python ───────────────────────────────
def check_response(resp):
    if resp.status_code == 200: return resp.json()
    elif resp.status_code == 401: raise PermissionError("Not authenticated")
    elif resp.status_code == 403: raise PermissionError("Not authorized")
    elif resp.status_code == 404: raise FileNotFoundError("Resource not found")
    elif resp.status_code == 429: raise RuntimeError("Rate limited — slow down")
    elif resp.status_code >= 500: raise RuntimeError(f"Server error: {resp.status_code}")
    else: resp.raise_for_status()

🏠 Index | SSL & TLS / OpenSSL →