About
netcat opens raw TCP or UDP connections and pipes data through them. It can also listen for an incoming connection. Use it to test a port, talk to a service by hand, or move one file between machines you control.
Install it
pkg install netcat-openbsd
Run this inside Termux. If the package is already present, pkg will say so and
do nothing.
Commands worth knowing
5 of the invocations you will actually reach for. Tap the copy button to put one on your clipboard.
nc -zv example.com 22 Test whether a single TCP port is open, without sending real data. A lightweight check on a host you manage. nc -lvnp 4444 Listen on port 4444 for one arriving connection. Handy for moving a file between your own machines. nc -w 3 example.com 80 Open a raw session to a web port. Type a request by hand and read the reply. nc -u -l 5353 Listen over UDP instead of TCP. Useful for debugging DNS and other datagram services. nc -zv -w 2 example.com 20-25 Sweep a small range of ports. A cheap pre-check before a deeper scan. Worked example
Run nc -zv -w 2 example.com 20-25 and this is what you should see.
$ nc -zv -w 2 example.com 20-25
Connection to example.com 20 port [tcp/ftp-data] succeeded!
Connection to example.com 21 port [tcp/ftp] succeeded!
Connection to example.com 22 port [tcp/ssh] succeeded!
Connection to example.com 23 port [tcp/telnet] refused Developed by
The OpenBSD project .