Week 13

Introduction to Netcat/Ncat and Basic Network Communication

Use Netcat/Ncat in an approved lab to test communication and basic file transfer between two systems.

Lesson recap

Netcat (`nc`, or its modern cousin Ncat that ships with Nmap) is the simplest possible network tool. One side listens on a port, the other connects, and now there's a pipe. Type into one terminal, the words appear in the other. Redirect a file in, the same bytes come out the far side. With Netcat you can test whether a firewall is open, transfer a file when nothing else works, and (in approved security labs) understand exactly how a reverse shell behaves. As with Nmap: useful in friendly hands, dangerous in hostile ones — and only legal on networks you own.

Learning goals

Explain what Netcat/Ncat does
Set up a listener and a client
Send a text message between two systems
Transfer a file between two systems
Document the test clearly

Key terms

Netcat / Ncat

The "Swiss Army knife" of networking — read/write data across network connections.

Listener

The side waiting for an incoming connection (server side).

Client

The side initiating the connection.

Loopback Test

A test on the same machine using 127.0.0.1.

Port

The numbered TCP/UDP endpoint both sides agree on.

Curated videos

Netcat Tutorial — Transfer Files

KMDTech

tcpdump — Traffic Capture & Analysis (companion tool)

HackerSploit

Commands

ncat -h

ncat -l 4444

ncat <listener-ip> 4444

ncat -l 4444 > received.txt

ncat <listener-ip> 4444 < tosend.txt

ncat -zv <listener-ip> 4444

ncat -lu 4444

Checkpoint checklist

Pro tips from the instructor

★Start the listener BEFORE the client. The client errors out instantly if no one is listening.
★Some firewalls block raw TCP on uncommon ports. Test with ports you know are open (8080, 4444) when troubleshooting.
★Use Ncat (from Nmap) instead of legacy netcat-traditional — Ncat works the same on Windows, Linux, and macOS.

Try this — stretch exercises

Optional hands-on practice that goes beyond the workbook. Check items off as you complete them — progress saves in this browser.

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Pipe a directory through tar over ncat: on the listener `ncat -l 4444 | tar xvf -`, on the sender `tar cvf - mydir/ | ncat receiver 4444`.
Run Wireshark while you do an ncat transfer. Watch the entire conversation in cleartext — that's why production transfers use SSH/SCP, not raw netcat.

Files to save this week

📁 Week13_NcatListener_YourLastName.png
📁 Week13_NcatClient_YourLastName.png
📁 Week13_NcatFileTransfer_YourLastName.png
📁 Week13_NcatReport_YourLastName