Chapter 6 — Session 2: Application Protocols & Ports — Part 1

Now we're moving into one of the biggest Network+ memorization sections:

Protocols + Port Numbers

We're not doing the entire protocol table at once. That would be way too much. We're starting with the first group.

📋 Topics to Mark Off

⬜ FTP
⬜ FTP TCP 20
⬜ FTP TCP 21
⬜ FTP Data vs. Control
⬜ SSH
⬜ SSH TCP 22
⬜ SFTP
⬜ SFTP TCP 22
⬜ Telnet
⬜ Telnet TCP 23
⬜ SMTP
⬜ SMTP TCP 25
⬜ Secure vs. Insecure Remote Access
⬜ Protocol Recognition by Port Number

These protocols are part of the Chapter 6 protocol/port section. Your source specifically emphasizes learning the protocol names and their associated port numbers.

📁 FTP — File Transfer Protocol

FTP = File Transfer Protocol

Its purpose:

Transfer files between systems.

Example:

💻 Computer │ │ FTP ↓ 🖥️ FTP Server Upload/download files

FTP is unusual because it commonly uses TWO ports:

TCP 20 + TCP 21

⭐ FTP Port 21

TCP 21 = CONTROL

This is used for the FTP control connection.

Think of this as the conversation between the client and server.

💻 Client ─── TCP 21 ───→ 🖥️ FTP Server ↑ CONTROL

Commands such as:

“Log me in.”

“I want this file.”

are part of the control side.

🧠 Memory

21 = FTP Control

⭐ FTP Port 20

TCP 20 = DATA

Think:

The actual file data

📄 FILE ↓ TCP 20 ↓ 💻

For your Network+ memorization:

FTP 20 = Data

FTP 21 = Control

🧠 FTP Memory Trick

Think:

20 → DATA
21 → CONTROL

Or:

FTP gets 20/21

This pair needs to become automatic.

🔐 SSH — Secure Shell

SSH = Secure Shell

SSH is used for:

Secure remote command-line access

Imagine you're sitting at your computer:

💻 You │ │ SSH ↓ 🖥️ Linux Server

You can remotely access the server's command line.

The important part:

🔐 SSH IS ENCRYPTED

SSH uses:

TCP 22

🧠 Memory

SSH = Secure = 22

📁 SFTP

SFTP = SSH File Transfer Protocol

SFTP allows:

Secure file transfers using SSH

And because it operates through SSH:

SFTP = TCP 22

SSH
 ↓
TCP 22
 ↓
SFTP

🧠 Big Connection

SSH + SFTP = 22

🚨 FTP vs. SFTP

This distinction matters.

FTP

File transfer
TCP 20/21

SFTP

SECURE file transfer
TCP 22

So if CompTIA says:

A technician needs to securely transfer files to a remote server.

Think:

✅ SFTP

Not ordinary FTP.

💻 Telnet

Telnet is also used for:

Remote command-line access

Sounds like SSH, right?

Yes.

But there's one MASSIVE difference.

🚨 TELNET IS NOT SECURE

Telnet sends information without the encryption SSH provides.

Telnet uses:

TCP 23

TELNET
   ↓
TCP 23
   ↓
Remote CLI

❌ NOT ENCRYPTED

🧠 Memory

Look at the numbers:

SSH      22 🔐
TELNET   23 😬

They're right next to each other.

🆚 SSH vs. Telnet — EXAM GOLD

SSH	Telnet
TCP 22	TCP 23
Remote CLI	Remote CLI
🔐 Encrypted	❌ Unencrypted
Secure	Insecure

This is a very testable distinction.

🚨 Scenario

A network administrator needs to remotely configure a Linux server across an untrusted network.

Which should they use?

SSH

Why?

Because SSH provides:

Encrypted remote command-line access

📧 SMTP

SMTP = Simple Mail Transfer Protocol

SMTP is associated with:

Sending email

SMTP uses:

TCP 25

Think:

📧 EMAIL ↓ SMTP ↓ TCP 25

🧠 Memory

SMTP = Send Mail

The letters aren't literally “Send Mail,” but that's a great way to remember its job.

📧 What SMTP Does

Think about mail servers communicating:

📧 Mail Server │ │ SMTP ↓ 📧 Mail Server

SMTP is used for transferring/sending email.

So if CompTIA asks:

Which protocol is associated with sending email?

✅ SMTP

🧠 The Number Pattern

Look at what you've learned:

FTP
20 / 21

SSH
22

TELNET
23

SMTP
25

That's actually pretty nice.

They're clustered together.

20 → FTP Data

21 → FTP Control

22 → SSH / SFTP

23 → Telnet

25 → SMTP

Notice we're only missing 24.

That makes this group easier to memorize.

⭐ Security Pattern

Another useful way to organize them:

SECURE

🔐 SSH TCP 22 SFTP TCP 22 NOT SECURE ❌ FTP TCP 20/21 Telnet TCP 23

Then:

EMAIL

📧 SMTP TCP 25

🚨 EXAM SCENARIO

A technician wants to transfer a configuration file to a server securely.

Options:

A. FTP
B. Telnet
C. SFTP
D. SMTP

✅ SFTP

The word securely is the clue.

🚨 EXAM SCENARIO

A technician discovers TCP port 23 open on a legacy network device.

What protocol should they suspect?

✅ Telnet

And immediately think:

Unencrypted remote access

🚨 EXAM SCENARIO

A firewall is blocking TCP 22.

Which services could be affected?

✅ SSH / SFTP

That's why you need to know the numbers both directions:

Not just:

SSH → 22

But also:

22 → SSH

🎴 Flashcards

⭐ 1 — EXAM GOLD

Which TCP ports are associated with FTP?

A. 21 and 22
B. 20 and 21
C. 22 and 23
D. 23 and 25

✅ B

⭐ 2

Which FTP port is traditionally associated with the control connection?

A. TCP 20
B. TCP 21
C. TCP 22
D. TCP 23

✅ B

🧠 21 = Control

⭐ 3

Which FTP port is traditionally associated with data transfer?

A. TCP 20

B. TCP 21

C. TCP 22

D. TCP 25

✅ A

🧠 20 = Data

⭐ 4 — EXAM GOLD

Which protocol provides encrypted remote command-line access?

A. FTP
B. SSH
C. Telnet
D. SMTP

✅ B

⭐ 5

Which port does SSH use?

A. TCP 20
B. TCP 21
C. TCP 22
D. TCP 23

✅ C

⭐ 6

Which protocol provides secure file transfers through SSH?

A. FTP

B. SFTP

C. SMTP

D. Telnet

✅ B

⭐ 7

Which port is associated with SFTP?

A. TCP 21

B. TCP 22

C. TCP 23

D. TCP 25

✅ B

⭐ 8 — EXAM GOLD

Which protocol provides unencrypted remote command-line access?

A. SSH

B. Telnet

C. SFTP

D. SMTP

✅ B

⭐ 9

Which port is associated with Telnet?

A. TCP 21

B. TCP 22

C. TCP 23

D. TCP 25

✅ C

⭐ 10 — Scenario

A security analyst discovers TCP 23 being used for remote administration.

Which protocol is MOST likely being used?

A. FTP

B. SSH

C. Telnet

D. SMTP

✅ C

⭐ 11 — EXAM GOLD

Which protocol is associated with sending email?

A. SSH

B. FTP

C. Telnet

D. SMTP

✅ D

⭐ 12

Which port is associated with SMTP?

A. TCP 22

B. TCP 23

C. TCP 25

D. TCP 53

✅ C

⭐ 13 — Scenario

A technician needs to securely transfer files to a Linux server.

Which protocol should be used?

A. FTP

B. Telnet

C. SFTP

D. SMTP

✅ C

⭐ 14 — Comparison

Which pair uses the same TCP port?

A. FTP and Telnet

B. SSH and SFTP

C. SMTP and FTP

D. Telnet and SMTP

✅ B — TCP 22

⭐ 15 — Scenario

A firewall administrator blocks TCP port 22.

Which two services could be affected?

A. FTP and SMTP

B. FTP and Telnet

C. SSH and SFTP

D. SMTP and Telnet

✅ C

🧠 Memory Board

📁 FTP File Transfer Protocol 20 = DATA 21 = CONTROL 🔐 SSH Secure remote CLI 22 🔐📁 SFTP Secure file transfer 22 💻 TELNET Remote CLI ❌ NOT SECURE 23 📧 SMTP SEND EMAIL 25

🎯 Know These Cold

FTP = TCP 20/21

FTP 20 = Data

FTP 21 = Control

SSH = TCP 22 + secure remote CLI

SFTP = TCP 22 + secure file transfer

Telnet = TCP 23 + unencrypted remote CLI

SMTP = TCP 25 + email

And especially:

🔐 SSH = 22

😬 Telnet = 23

Those two sitting right next to each other are an easy place for CompTIA to test you.

FTP (File Transfer Protocol)

Data Port = TCP 20

Control Port = TCP 21

SMTP (Simple Mail Transfer Protocol)

SMTP = Send mail = Port 25

SFTP = Secure File Transfer = Port 22

SSH = Port 22