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 indefinitely,
       until the network side of the connection shuts down.  Note that this behavior is different
       from  most  other applications 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 copyrights 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)