NC(1)                                                    General Commands Manual                                                   NC(1)

NAME
       nc - TCP/IP swiss army knife

SYNOPSIS
       nc [-options] hostname port[s] [ports] ...
       nc -l -p port [-options] [hostname] [port]

DESCRIPTION
       netcat is a simple unix utility which reads and writes data across network connections, using TCP or UDP protocol. It is designed
       to be a reliable "back-end" tool that can be used directly or easily driven by other programs and scripts.  At the same time,  it
       is  a  feature-rich  network debugging and exploration tool, since it can create almost any kind of connection you would need and
       has several interesting built-in capabilities.  Netcat, or "nc" as the actual program is named, should have  been  supplied  long
       ago as another one of those cryptic but standard Unix tools.

       In  the  simplest usage, "nc host port" creates a TCP connection to the given port on the given target host.  Your standard input
       is then sent to the host, and anything that comes back across the connection is sent to your standard output.  This continues in‐
       definitely,  until  the network side of the connection shuts down.  Note that this behavior is different from most other applica‐
       tions which shut everything down and exit after an end-of-file on the standard input.

       Netcat can also function as a server, by listening for inbound connections on arbitrary ports and then doing the same reading and
       writing.   With  minor  limitations,  netcat doesn't really care if it runs in "client" or "server" mode -- it still shovels data
       back and forth until there isn't any more left. In either mode, shutdown can be forced after a configurable time of inactivity on
       the network side.

       And  it  can do this via UDP too, so netcat is possibly the "udp telnet-like" application you always wanted for testing your UDP-
       mode servers.  UDP, as the "U" implies, gives less reliable data transmission than TCP connections  and  some  systems  may  have
       trouble sending large amounts of data that way, but it's still a useful capability to have.

       You may be asking "why not just use telnet to connect to arbitrary ports?" Valid question, and here are some reasons.  Telnet has
       the "standard input EOF" problem, so one must introduce calculated delays in driving scripts to allow network output  to  finish.
       This  is  the  main  reason netcat stays running until the *network* side closes.  Telnet also will not transfer arbitrary binary
       data, because certain characters are interpreted as telnet options and are thus removed from the data stream.  Telnet also  emits
       some  of  its  diagnostic messages to standard output, where netcat keeps such things religiously separated from its *output* and
       will never modify any of the real data in transit unless you *really* want it to.  And of course telnet is incapable of listening
       for  inbound  connections,  or  using UDP instead.  Netcat doesn't have any of these limitations, is much smaller and faster than
       telnet, and has many other advantages.

OPTIONS
       -c string    specify shell commands to exec after connect (use with caution).  The string is passed to /bin/sh -c for  execution.
                    See the -e option if you don't have a working /bin/sh (Note that POSIX-conformant system must have one).

       -e filename  specify filename to exec after connect (use with caution).  See the -c option for enhanced functionality.

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

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

       -h           display help

       -i secs      delay interval for lines sent, ports scanned

       -l           listen mode, for inbound connects

       -n           numeric-only IP addresses, no DNS

       -o file      hex dump of traffic

       -p port      local port number (port numbers can be individual or ranges: lo-hi [inclusive])

       -q seconds   after EOF on stdin, wait the specified number of seconds and then quit. If seconds is negative, wait forever.

       -b           allow UDP broadcasts

       -r           randomize local and remote ports

       -s addr      local source address

       -t           enable 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]

       -T type      set  TOS  flag  (type  may  be one of "Minimize-Delay", "Maximize-Throughput", "Maximize-Reliability", or "Minimize-
                    Cost".)

COPYRIGHT
       Netcat is entirely my own creation, although plenty of other code was used as examples.  It is freely given away to the  Internet
       community in the hope that it will be useful, with no restrictions except giving credit where it is due.  No GPLs, Berkeley copy‐
       rights or any of that nonsense.  The author assumes NO responsibility for how anyone uses it.  If netcat makes you  rich  somehow
       and  you're  feeling generous, mail me a check.  If you are affiliated in any way with Microsoft Network, get a life.  Always ski
       in control.  Comments, questions, and patches to hobbit@avian.org.

NOTES
       Some port names in /etc/services contain hyphens -- netcat currently will not correctly parse those unless you escape the hyphens
       with backslashes (e.g. "netcat localhost 'ftp\-data'").

BUGS
       Efforts  have  been made to have netcat "do the right thing" in all its various modes.  If you believe that it is doing the wrong
       thing under whatever circumstances, please notify me and tell me how you think it should behave.  If netcat is  not  able  to  do
       some  task  you  think up, minor tweaks to the code will probably fix that.  It provides a basic and easily-modified template for
       writing other network applications, and I certainly encourage people to make custom mods and send in any improvements  they  make
       to it. Continued feedback from the Internet community is always welcome!

EXAMPLES
       For several netcat recipes, please see /usr/share/doc/netcat/README.gz and /usr/share/doc/netcat/README.Debian.gz.

AUTHOR
       This manual page was written by Joey Hess <joeyh@debian.org> and Robert Woodcock <rcw@debian.org>, cribbing heavily from Netcat's
       README file.

       Netcat was written by a guy we know as the Hobbit <hobbit@avian.org>.

                                                                                                                                   NC(1)

[v1.10-41.1]
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]
port numbers can be individual or ranges: lo-hi [inclusive];
hyphens in port names must be backslash escaped (e.g. 'ftp\-data').