Ncat

Ncat is improved reimplementation of not anymore maintained netcat software by nmap developers. It Includes support for chain Ncats together, redirect both TCP and UDP ports to other sites, SSL support, and proxy connections via SOCKS4 or HTTP (CONNECT method) proxies (with optional proxy authentication as well).

Usage examples

• Connect to example.org on TCP port 8080. : ncat example.org 8080
• Listen for connections on TCP port 8080. : ncat -l 8080
• Redirect TCP port 8080 on the local machine to host on port 80. : ncat --sh-exec "ncat example.org 80" -l 8080 --keep-open
• Bind to TCP port 8081 and attach /bin/bash for the world to access freely. : ncat --exec "/bin/bash" -l 8081 --keep-open
• Bind a shell to TCP port 8081, limit access to hosts on a local network, and limit the maximum number of simultaneous connections to 3:

ncat --exec "/bin/bash" --max-conns 3 --allow 192.168.0.0/24 -l 8081 --keep-open

• Connect to smtphost:25 through a SOCKS4 server on port 1080: ncat --proxy socks4host --proxy-type socks4 --proxy-auth user smtphost 25
• Create an HTTP proxy server on localhost port 8888. : ncat -l --proxy-type http localhost 8888
• Send a file over TCP port 9899 from host2 (client) to host1 (server).<syntaxhighlight lang="console">

user@HOST1$ ncat -l 9899 > outputfile user@HOST2$ ncat HOST1 9899 < inputfile </syntaxhighlight>

• Transfer in the other direction, turning Ncat into a “one file” server.<syntaxhighlight lang="console">

user@HOST1$ ncat -l 9899 < inputfile user@HOST2$ ncat HOST1 9899 > outputfile </syntaxhighlight>

See also

• cat
• ssh (OpenSSH client)