netcat (nc): The Swiss Army Knife of Networking
netcat (nc) does one thing: move bytes over a network. That simplicity makes it incredibly versatile — port scanning, file transfers, chat servers, proxies, and network debugging all become one-liners. Basic Usage 1 2 3 4 5 6 7 8 # Connect to host:port nc hostname 80 # Listen on port nc -l 8080 # Listen (keep listening after disconnect) nc -lk 8080 Test if Port is Open 1 2 3 4 5 6 7 8 9 # Quick port check nc -zv hostname 22 # Connection to hostname 22 port [tcp/ssh] succeeded! # Scan port range nc -zv hostname 20-25 # With timeout nc -zv -w 3 hostname 443 Simple Client-Server Communication Server (listener) 1 nc -l 9000 Client 1 nc localhost 9000 Now type in either terminal — text flows both ways. Ctrl+C to exit. ...