Linux in a Nutshell, 6th Edition

Name

nc

Synopsis

nc [options] [host] [port]

TCP/IP command. nc (also known as netcat) is a versatile networking utility that reads and writes data across network connections using TCP or UDP. It’s a simple tool that has many uses. Unlike telnet, you can easily script nc. It can also be used to listen for as well as make connections.

Options

-C

Send CRLF as line ending.

-i seconds

Send and read data one line at a time with a delay of the specified interval in seconds. By default netcat reads and writes in 8 KB blocks.

-k

Listen for further connections when a current connection ends. Used with -l.

-l

Listen for an incoming connection on the specified port or ports.

-n

Don’t perform any DNS lookups.

-o file

Hex-dump data sent and received to file.

-p [port]

Read from the specified source port.

-r

Choose ports randomly.

-s [address]

Read from the specified source IP address.

-u

Use UDP instead of the default TCP.

-U

Use Unix Domain Sockets instead of the default TCP.

-v

Verbose output. Use multiple times to increase verbosity. If not using -n, include reports on forward/reverse DNS mismatches.

-w seconds

Set the inactivity timeout for a connection. Silently close a connection if idle for more than the specified seconds.

-x address[:port]

Use the proxy found at the specified IP address and port. If no port is specified, the well-known port for the protocol is used.

-X protocol

Use the specified proxy protocol. Valid values are 4 (SOCKS v. 4), 5 (SOCKS v. 5) and connect (HTTPS proxy). The default value is 5.

-z

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