Network Protocols Cheatsheet: Essential IT Reference

You Should Know:

1. HTTP/HTTPS

 Check HTTP headers using curl 
curl -I http://example.com

Test HTTPS/TLS configuration 
openssl s_client -connect example.com:443 -servername example.com 

2. WebSocket

 WebSocket connection test (using wscat) 
npm install -g wscat 
wscat -c ws://echo.websocket.org 

3. FTP

 Connect to FTP server 
ftp ftp.example.com

Download file via FTP 
wget ftp://ftp.example.com/file.zip 

4. TCP/UDP

 Check open TCP ports 
netstat -tuln

Test UDP connectivity 
nc -u <host> <port> 

5. SMTP

 Test email server 
telnet smtp.example.com 25 
EHLO example.com 
MAIL FROM: <a href="mailto:sender@example.com">sender@example.com</a> 
RCPT TO: <a href="mailto:receiver@example.com">receiver@example.com</a> 
DATA 
Subject: Test 
This is a test email. 
. 
QUIT 

6. QUIC (HTTP/3)

 Check HTTP/3 support (using curl 7.66+) 
curl --http3 https://example.com 

7. Encryption (Public/Session Keys)

 Generate SSH key pair 
ssh-keygen -t ed25519

Encrypt file with OpenSSL 
openssl enc -aes-256-cbc -salt -in file.txt -out file.enc 

8. Full-Duplex Communication

 Create a bidirectional chat with netcat 
nc -l -p 1234  Terminal 1 
nc localhost 1234  Terminal 2 

What Undercode Say

Mastering protocols is critical for IT/cybersecurity. Practice these commands:
– Linux: `tcpdump -i eth0 ‘tcp port 80’` (Monitor HTTP traffic).
– Windows: `Test-NetConnection -ComputerName example.com -Port 443` (Check HTTPS).
– Security: Always use `HTTPS` over HTTP, enforce TLS 1.3, and disable weak ciphers.

Prediction

HTTP/3 (QUIC) will dominate by 2025 due to its speed and encryption.

Expected Output

HTTP/1.1 200 OK 
Server: nginx 
Date: [bash] 
Content-Type: text/html 

For more: Mozilla HTTP Guide

References:

Reported By: Satya619 Network – Hackers Feeds
Extra Hub: Undercode MoN
Basic Verification: Pass ✅

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