$ nc -h
OpenBSD netcat (Debian patchlevel 1.105-7ubuntu1)
This is nc from the netcat-openbsd package. An alternative nc is available
in the netcat-traditional package.
usage: nc [-46bCDdhjklnrStUuvZz] [-I length] [-i interval] [-O length]
  [-P proxy_username] [-p source_port] [-q seconds] [-s source]
  [-T toskeyword] [-V rtable] [-w timeout] [-X proxy_protocol]
  [-x proxy_address[:port]] [destination] [port]
 Command Summary:
  -4  Use IPv4
  -6  Use IPv6
  -b  Allow broadcast
  -C  Send CRLF as line-ending
  -D  Enable the debug socket option
  -d  Detach from stdin
  -h  This help text
  -I length TCP receive buffer length
  -i secs  Delay interval for lines sent, ports scanned
  -j  Use jumbo frame
  -k  Keep inbound sockets open for multiple connects
  -l  Listen mode, for inbound connects
  -n  Suppress name/port resolutions
  -O length TCP send buffer length
  -P proxyuser Username for proxy authentication
  -p port  Specify local port for remote connects
   -q secs  quit after EOF on stdin and delay of secs
  -r  Randomize remote ports
  -S  Enable the TCP MD5 signature option
  -s addr  Local source address
  -T toskeyword Set IP Type of Service
  -t  Answer TELNET negotiation
  -U  Use UNIX domain socket
  -u  UDP mode
  -V rtable Specify alternate routing table
  -v  Verbose
  -w secs  Timeout for connects and final net reads
  -X proto Proxy protocol: "4", "5" (SOCKS) or "connect"
  -x addr[:port] Specify proxy address and port
  -Z  DCCP mode
  -z  Zero-I/O mode [used for scanning]
 Port numbers can be individual or ranges: lo-hi [inclusive]

$ nc -z -v -n 127.0.0.1 20-100
...
Connection to 127.0.0.1 80 port [tcp/*] succeeded!
...

$ nc -l 192.168.1.11 1234 > passwd.txt &

$ nc 192.168.1.11 1234 < /etc/passwd

cat /etc/passwd | nc 192.168.1.11 1234