nc -h:

connect to somewhere:	nc [-options] hostname port[s] [ports] ...

listen for inbound:	nc -l -p port [-options] [hostname] [port]

options:

	-c shell commands	as `-e'; use /bin/sh to exec [dangerous!!]

	-e filename		program to exec after connect [dangerous!!]

	-b			allow broadcasts

	-g gateway		source-routing hop point[s], up to 8

	-G num			source-routing pointer: 4, 8, 12, ...

	-h			this cruft

	-i secs			delay interval for lines sent, ports scanned

        -k                      set keepalive option on socket

	-l			listen mode, for inbound connects

	-n			numeric-only IP addresses, no DNS

	-o file			hex dump of traffic

	-p port			local port number

	-r			randomize local and remote ports

	-q secs			quit after EOF on stdin and delay of secs

	-s addr			local source address

	-T tos			set Type Of Service

	-t			answer TELNET negotiation

	-u			UDP mode

	-v			verbose [use twice to be more verbose]

	-w secs			timeout for connects and final net reads

	-C			Send CRLF as line-ending

	-z			zero-I/O mode [used for scanning]

Usage: ncat [options] [hostname] [port]

Options taking a time assume seconds. Append 'ms' for milliseconds,

's' for seconds, 'm' for minutes, or 'h' for hours (e.g. 500ms).

  -4                         Use IPv4 only

  -6                         Use IPv6 only

  -U, --unixsock             Use Unix domain sockets only

  -C, --crlf                 Use CRLF for EOL sequence

  -c, --sh-exec <command>    Executes the given command via /bin/sh

  -e, --exec <command>       Executes the given command

      --lua-exec <filename>  Executes the given Lua script

  -g hop1[,hop2,...]         Loose source routing hop points (8 max)

  -G <n>                     Loose source routing hop pointer (4, 8, 12, ...)

  -m, --max-conns <n>        Maximum <n> simultaneous connections

  -h, --help                 Display this help screen

  -d, --delay <time>         Wait between read/writes

  -o, --output <filename>    Dump session data to a file

  -x, --hex-dump <filename>  Dump session data as hex to a file

  -i, --idle-timeout <time>  Idle read/write timeout

  -p, --source-port port     Specify source port to use

  -s, --source addr          Specify source address to use (doesn't affect -l)

  -l, --listen               Bind and listen for incoming connections

  -k, --keep-open            Accept multiple connections in listen mode

  -n, --nodns                Do not resolve hostnames via DNS

  -t, --telnet               Answer Telnet negotiations

  -u, --udp                  Use UDP instead of default TCP

      --sctp                 Use SCTP instead of default TCP

  -v, --verbose              Set verbosity level (can be used several times)

  -w, --wait <time>          Connect timeout

  -z                         Zero-I/O mode, report connection status only

      --append-output        Append rather than clobber specified output files

      --send-only            Only send data, ignoring received; quit on EOF

      --recv-only            Only receive data, never send anything

      --allow                Allow only given hosts to connect to Ncat

      --allowfile            A file of hosts allowed to connect to Ncat

      --deny                 Deny given hosts from connecting to Ncat

      --denyfile             A file of hosts denied from connecting to Ncat

      --broker               Enable Ncat's connection brokering mode

      --chat                 Start a simple Ncat chat server

      --proxy <addr[:port]>  Specify address of host to proxy through

      --proxy-type <type>    Specify proxy type ("http" or "socks4" or "socks5")

      --proxy-auth <auth>    Authenticate with HTTP or SOCKS proxy server

      --ssl                  Connect or listen with SSL

      --ssl-cert             Specify SSL certificate file (PEM) for listening

      --ssl-key              Specify SSL private key (PEM) for listening

      --ssl-verify           Verify trust and domain name of certificates

      --ssl-trustfile        PEM file containing trusted SSL certificates

      --ssl-ciphers          Cipherlist containing SSL ciphers to use

      --ssl-alpn             ALPN protocol list to use.

      --version              Display Ncat's version information and exit