Netcat Command Cheat Sheet

This resource provides you with the common and useful commands when working with the netcat utility.

Basic Usage

Banner Grabbing

Port Scanning

File Transfer

Directory Transfer

Remote Shell

Reverse Shell

Video Stream

Netcat Command Options

The following are some popular command options.

     The options are as follows:

     -4      Use IPv4 addresses only.

     -6      Use IPv6 addresses only.

     -b      Allow broadcast.

     -C      Send CRLF as line-ending.  Each line feed (LF) character from the input data is translated into CR+LF before being written to the socket.  Line feed characters that are already preceded with a carriage return (CR) are not translated.  Received data is not
             affected.

     -D      Enable debugging on the socket.

     -d      Do not attempt to read from stdin.

     -F      Pass the first connected socket using sendmsg(2) to stdout and exit.  This is useful in conjunction with -X to have nc perform connection setup with a proxy but then leave the rest of the connection to another program (e.g. ssh(1) using the ssh_config(5)
             ProxyUseFdpass option).  Cannot be used with -U.

     -h      Print out the nc help text and exit.

     -I length
             Specify the size of the TCP receive buffer.

     -i interval
             Sleep for interval seconds between lines of text sent and received.  Also causes a delay time between connections to multiple ports.

     -k      When a connection is completed, listen for another one.  Requires -l.  When used together with the -u option, the server socket is not connected and it can receive UDP datagrams from multiple hosts.

     -l      Listen for an incoming connection rather than initiating a connection to a remote host.  The destination and port to listen on can be specified either as non-optional arguments, or with options -s and -p respectively.  Cannot be used together with -x or -z.
             Additionally, any timeouts specified with the -w option are ignored.

     -M ttl  Set the TTL / hop limit of outgoing packets.

     -m minttl
             Ask the kernel to drop incoming packets whose TTL / hop limit is under minttl.

     -N      shutdown(2) the network socket after EOF on the input.  Some servers require this to finish their work.

     -n      Do not perform domain name resolution.  If a name cannot be resolved without DNS, an error will be reported.

     -O length
             Specify the size of the TCP send buffer.

     -P proxy_username
             Specifies a username to present to a proxy server that requires authentication.  If no username is specified then authentication will not be attempted.  Proxy authentication is only supported for HTTP CONNECT proxies at present.

     -p source_port
             Specify the source port nc should use, subject to privilege restrictions and availability.

     -q seconds
             after EOF on stdin, wait the specified number of seconds and then quit. If seconds is negative, wait forever (default).  Specifying a non-negative seconds implies -N.

     -r      Choose source and/or destination ports randomly instead of sequentially within a range or in the order that the system assigns them.

     -S      Enable the RFC 2385 TCP MD5 signature option.

     -s sourceaddr
             Set the source address to send packets from, which is useful on machines with multiple interfaces.  For UNIX-domain datagram sockets, specifies the local temporary socket file to create and use so that datagrams can be received.  Cannot be used together
             with -x.

     -T keyword
             Change the IPv4 TOS/IPv6 traffic class value.  keyword may be one of critical, inetcontrol, lowcost, lowdelay, netcontrol, throughput, reliability, or one of the DiffServ Code Points: ef, af11 ... af43, cs0 ... cs7; or a number in either hex or decimal.

     -t      Send RFC 854 DON'T and WON'T responses to RFC 854 DO and WILL requests.  This makes it possible to use nc to script telnet sessions.

     -U      Use UNIX-domain sockets.  Cannot be used together with -F or -x.

     -u      Use UDP instead of TCP.  Cannot be used together with -x.  For UNIX-domain sockets, use a datagram socket instead of a stream socket.  If a UNIX-domain socket is used, a temporary receiving socket is created in /tmp unless the -s flag is given.

     -V rtable
             Set the routing table to be used.

     -v      Produce more verbose output.

     -W recvlimit
             Terminate after receiving recvlimit packets from the network.

     -w timeout
             Connections which cannot be established or are idle timeout after timeout seconds.  The -w flag has no effect on the -l option, i.e. nc will listen forever for a connection, with or without the -w flag.  The default is no timeout.

     -X proxy_protocol
             Use proxy_protocol when talking to the proxy server.  Supported protocols are 4 (SOCKS v.4), 5 (SOCKS v.5) and connect (HTTPS proxy).  If the protocol is not specified, SOCKS version 5 is used.

     -x proxy_address[:port]
             Connect to destination using a proxy at proxy_address and port.  If port is not specified, the well-known port for the proxy protocol is used (1080 for SOCKS, 3128 for HTTPS).  An IPv6 address can be specified unambiguously by enclosing proxy_address in
             square brackets.  A proxy cannot be used with any of the options -lsuU.

     -Z      DCCP mode.

     -z      Only scan for listening daemons, without sending any data to them.  Cannot be used together with -l.

Conclusion

This is a short cheat sheet with the most common and useful netcat commands and examples. Thanks for reading. Feel free to grab a feel PDF copy of this cheat sheet in the resource below.

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