Linux Netcat NC Commandhttp://mylinuxbook.com/linux-netcat-command/http://www.thegeekstuff.com/2012/04/nc-command-examples/1. Port scanning
$nc -z -v -n 172.31.100.7 21-25
z option tell netcat to use zero IO .i.e the connection is closed as soon as it opens and no actual data exchange take place.
n option tell netcat not to use the DNS lookup for the address.
The netcat utility can be run in the server mode on a specified port listening for incoming connections.
$ nc -l 2389
Also, it can be used in client mode trying to connect on the port(2389) just opened
$ nc localhost 2389
Use Netcat to Transfer Files
we run the server as :
$ nc -l 2389 > test
and run the client as :
cat testfile | nc localhost 2389
Server
$nc -l 1567 < file.txt
Client
$nc -n 172.31.100.7 1567 > file.txt
Server
$nc -l 1567 > file.txt
Client
$nc 172.31.100.23 1567 < file.txt
4. Directory transfer
Server
$tar -cvf – dir_name | nc -l 1567
Client
$nc -n 172.31.100.7 1567 | tar -xvf
Server
$tar -cvf – dir_name| bzip2 -z | nc -l 1567
Compress the archive using the bzip2 utility.
Client
$nc -n 172.31.100.7 1567 | bzip2 -d |tar -xvf -
7. Cloning a device
Server
$dd if=/dev/sda | nc -l 1567
Client
$nc -n 172.31.100.7 1567 | dd of=/dev/sda
dd is a tool which reads the raw data from the disk
8. Opening a shell
Server
$nc -l 1567 -e /bin/bash -i
Client
$nc 172.31.100.7 1567
$nc 172.31.100.7 1567 -p 25
$nc -u 172.31.100.7 1567 -s 172.31.100.5 > file.txt
Netcat Supports Timeouts
nc -w 10 localhost 2389
The connection above would be terminated after 10 seconds.
Force Netcat Server to Stay Up
This behavior can be controlled by using the -k flag at the server side to force the server to stay up even after the client has disconnected.
$ nc -k -l 2389
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