nc Command
Advanced Networking man(1)Networking utility for reading/writing across network connections
👁 119 views
📅 Updated: Apr 29, 2026
SYNTAX
nc [OPTION]... [HOST] [PORT]
What Does nc Do?
nc (netcat) is a versatile networking utility that reads and writes data across network connections. It can create TCP/UDP connections, listen for connections, port scan, transfer files, and serve as a network debugging tool.
nc is often called the "Swiss Army knife" of networking. It can function as a simple client or server for any protocol, making it invaluable for testing, debugging, and ad-hoc data transfer.
nc is commonly used for port checking, quick file transfers, network chat, and as a building block in shell scripts for network operations.
nc is often called the "Swiss Army knife" of networking. It can function as a simple client or server for any protocol, making it invaluable for testing, debugging, and ad-hoc data transfer.
nc is commonly used for port checking, quick file transfers, network chat, and as a building block in shell scripts for network operations.
Options & Flags
| Option | Description | Example |
|---|---|---|
| -l | Listen mode (server) | nc -l 8080 |
| -v | Verbose output | nc -v example.com 80 |
| -z | Scan mode (zero I/O, for port scanning) | nc -zv example.com 80 |
| -w | Timeout in seconds | nc -w 3 example.com 80 |
| -u | UDP mode | nc -u example.com 53 |
| -k | Keep listening after client disconnects | nc -lk 8080 |
Practical Examples
#1 Check if port is open
Tests if port 443 is open on the remote host.
$ nc -zv example.com 443
Output:
Connection to example.com 443 port [tcp/https] succeeded!
#2 Scan port range
Scans ports 20-25 on the remote host.
$ nc -zv example.com 20-25#3 Simple chat server
Listens on port 9000 — anything typed on the other end appears here.
$ nc -l 9000#4 Connect to chat
Connects to the listening nc and enables text exchange.
$ nc hostname 9000#5 File transfer (receiver)
Receives a file on port 9000.
$ nc -l 9000 > received_file.tar.gz#6 File transfer (sender)
Sends a file to the receiving nc.
$ nc hostname 9000 < file.tar.gz#7 HTTP request
Sends a raw HTTP request — useful for debugging web servers.
$ echo -e "GET / HTTP/1.1\r\nHost: example.com\r\n\r\n" | nc example.com 80#8 Port check in script
Checks if PostgreSQL is reachable with a 3-second timeout.
$ nc -zw3 db-server 5432 && echo "PostgreSQL up" || echo "PostgreSQL down"Tips & Best Practices
Quick port check: nc -zv host port is the fastest way to test if a remote port is open. Faster and simpler than telnet.
ncat vs nc variants: There are several nc variants: GNU netcat, OpenBSD netcat, ncat (from nmap). Options vary. Check nc -h for your version.
Security tool: nc can create reverse shells and transfer data. It is a legitimate admin tool but can be used maliciously — use responsibly.
Frequently Asked Questions
How do I check if a port is open?
nc -zv hostname port. It reports success or failure. Add -w 3 for a 3-second timeout.
How do I transfer a file with nc?
Receiver: nc -l 9000 > file. Sender: nc hostname 9000 < file. Simple and fast for quick transfers.
What is netcat used for?
Port checking, network debugging, file transfer, banner grabbing, and as a lightweight TCP/UDP client/server.
Related Commands
More Networking Commands
Download Networking Cheat Sheet
View all 31 Linux command cheat sheets →Master Linux with Professional eBooks
Curated IT eBooks covering Linux, DevOps, Cloud, and more
Browse Books →