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  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

       -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>.

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