Annotation of src/usr.bin/nc/nc.1, Revision 1.6
1.6 ! aaron 1: .\" $OpenBSD: nc.1,v 1.5 1998/09/28 06:57:35 millert Exp $
1.1 deraadt 2: .\"
3: .\" Copyright (c) 1996 David Sacerdote
4: .\" All rights reserved.
5: .\"
6: .\" Redistribution and use in source and binary forms, with or without
7: .\" modification, are permitted provided that the following conditions
8: .\" are met:
9: .\" 1. Redistributions of source code must retain the above copyright
10: .\" notice, this list of conditions and the following disclaimer.
11: .\" 2. Redistributions in binary form must reproduce the above copyright
12: .\" notice, this list of conditions and the following disclaimer in the
13: .\" documentation and/or other materials provided with the distribution.
14: .\" 3. The name of the author may not be used to endorse or promote products
15: .\" derived from this software without specific prior written permission
16: .\"
17: .\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
18: .\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
19: .\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
20: .\" IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
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28: .Dd August 1, 1996
1.3 aaron 29: .Dt NC 1
1.4 deraadt 30: .Os
1.1 deraadt 31: .Sh NAME
32: .Nm nc
1.5 millert 33: .Nd "arbitrary TCP and UDP connections and listens"
1.2 deraadt 34: .Sh SYNOPSIS
1.1 deraadt 35: .Nm nc
36: .Op Fl e Ar command
37: .Op Fl g Ar intermediates
38: .Op Fl G Ar hopcount
39: .Op Fl i Ar interval
40: .Op Fl lnrtuvz
41: .Op Fl o Ar filename
1.6 ! aaron 42: .Op Fl p Ar source port
1.1 deraadt 43: .Op Fl s Ar ip address
1.6 ! aaron 44: .Op Fl w Ar timeout
1.1 deraadt 45: .Op Ar hostname
46: .Op Ar port[s...]
47: .Sh DESCRIPTION
48: The
1.6 ! aaron 49: .Nm
1.1 deraadt 50: (or
51: .Nm netcat )
52: utility is used for just about anything under the sun
1.3 aaron 53: involving TCP or UDP. It can open TCP connections, send UDP packets,
54: listen on arbitrary TCP and UDP ports, do port scanning, and source
1.1 deraadt 55: routing. Unlike
56: .Xr telnet 1 ,
1.6 ! aaron 57: .Nm
1.1 deraadt 58: scripts nicely, and separates error messages onto standard error instead
1.6 ! aaron 59: of sending them to standard output, as
! 60: .Xr telnet 1
! 61: does with some.
1.1 deraadt 62: .Pp
63: Destination ports can be single integers, names as listed in
1.5 millert 64: .Xr services 5 ,
1.1 deraadt 65: or ranges. Ranges are in the form nn-mm, and several separate ports and/or
66: ranges may be specified on the command line.
67: .Pp
68: Common uses include:
1.6 ! aaron 69: .Bl -bullet
1.1 deraadt 70: .It
1.3 aaron 71: simple TCP proxies
1.1 deraadt 72: .It
1.3 aaron 73: shell\-script based HTTP clients and servers
1.1 deraadt 74: .It
75: network daemon testing
76: .It
77: source routing based connectivity testing
78: .It
79: and much, much more
80: .El
81: .Pp
82: The options are as follows:
83: .Bl -tag -width Ds
84: .It Fl e Ar command
85: Execute the specified command, using data from the network for stdin,
86: and sending stdout and stderr to the network. This option is only present if
1.6 ! aaron 87: .Nm
1.1 deraadt 88: was compiled with the GAPING_SECURITY_HOLE compile time option, since it
89: allows users to make arbitrary programs available to anyone on the network.
90: .It Fl g Ar intermediate-host
91: Specifies a hop along a loose source routed path. Can be used more than
92: once to build a chain of hop points.
93: .It Fl G Ar pointer
94: Positions the "hop counter" within the list of machines in the path of
95: a source routed packet. Must be a multiple of 4.
96: .It Fl i Ar seconds
97: Specifies a delay time interval between lines of text sent and received.
98: Also causes a delay time between connections to multiple ports.
99: .It Fl l
100: Is used to specify that
1.6 ! aaron 101: .Nm
1.1 deraadt 102: should listen for an incoming connection, rather than initiate a
1.3 aaron 103: connection to a remote host. Any hostname/IP address and port arguments
1.1 deraadt 104: restrict the source of inbound connections to only that address and
105: source port.
106: .It Fl n
107: Do not do DNS lookups on any of the specified addresses or hostnames, or
108: names of port numbers from /etc/services.
109: .It Fl o Ar filename
110: Create a hexadecimal log of data transferred in the specified file.
1.3 aaron 111: Each line begins with ``<'' or ``>''. ``<'' means "from the net" and ``>''
112: means "to the net".
1.1 deraadt 113: .It Fl p Ar port
114: Specifies the source port
1.6 ! aaron 115: .Nm
1.1 deraadt 116: should use, subject to privilege restrictions and availability.
117: .It Fl r
1.3 aaron 118: Specifies that source and/or destination ports should be chosen semi-randomly
1.1 deraadt 119: instead of sequentially within a range or in the order that the
120: system assigns.
121: .It Fl s Ar hostname/ip-address
1.3 aaron 122: Specifies the IP of the interface which is used to send the packets.
123: On some platforms, this can be used for UDP spoofing by using
124: .Xr ifconfig 8
125: to bring up a dummy interface with the desired source IP address.
1.1 deraadt 126: .It Fl t
127: Causes
1.6 ! aaron 128: .Nm
1.1 deraadt 129: to send RFC854 DON'T and WON'T responses to RFC854 DO
130: and WILL requests. This makes it possible to use
1.6 ! aaron 131: .Nm
1.1 deraadt 132: to script telnet sessions. The presence of this option can be
133: enabled or disabled as a compile-time option.
134: .It Fl u
1.6 ! aaron 135: Use UDP instead of TCP.
1.1 deraadt 136: On most platforms,
1.6 ! aaron 137: .Nm
1.1 deraadt 138: will behave as if a connection is established until it receives an
139: ICMP packet indicating that there is no program listening to what it
140: sends.
141: .It Fl v
142: Verbose. Cause
1.6 ! aaron 143: .Nm
1.3 aaron 144: to display connection information. Using
145: .Fl v
1.1 deraadt 146: more than once will cause
1.6 ! aaron 147: .Nm
1.1 deraadt 148: to become even more verbose.
149: .It Fl w Ar timeout
150: Specifies the number of seconds
1.6 ! aaron 151: .Nm
1.1 deraadt 152: should wait before deciding that
153: an attempt to establish a connection is hopeless.
154: Also used to specify how long to wait for more network data after standard
155: input closes.
156: .It Fl z
157: Specifies that
1.6 ! aaron 158: .Nm
1.1 deraadt 159: should just scan for listening
160: daemons, without sending any data to them. Diagnostic messages about refused
161: connections will not be
1.3 aaron 162: displayed unless
163: .Fl v
164: is specified twice.
1.1 deraadt 165: .Sh EXAMPLES
166: .Bl -tag -width x
167: .It Li "nc"
168: Wait for the user to type what would normally be command-line
169: arguments in at stdin.
170: .It Li "nc example.host 42"
171: Open a TCP connection to port 42 of example.host. If the connection
172: fails, do not display any error messages, but simply exit.
173: .It Li "nc -p 31337 example.host 42"
174: Open a TCP connection to port 42 of example.host, and use port 31337
175: as the source port.
176: .It Li "nc -w 5 example.host 42"
1.3 aaron 177: Open a TCP connection to port 42 of example.host, and time out after
1.1 deraadt 178: five seconds while attempting to connect.
179: .It Li "nc -u example.host 53"
180: Send any data from stdin
181: to UDP port 53 of example.host, and display any data returned.
182: .It Li "nc -s 10.1.2.3 example.host 42"
1.3 aaron 183: Open a TCP connection to port 42 of example.host using 10.1.2.3 as the
184: IP for the local end of the connection.
1.1 deraadt 185: .It Li "nc -v example.host 42"
1.3 aaron 186: Open a TCP connection to port 42 of example.host, displaying some
1.1 deraadt 187: diagnostic messages on stderr.
188: .It Li "nc -v -v example.host 42"
1.3 aaron 189: Open a TCP connection to port 42 of example.host, displaying all
1.1 deraadt 190: diagnostic messages on stderr.
191: .It Li "nc -v -z example.host 20-30"
1.3 aaron 192: Attempt to open TCP connections to ports 20 through 30 of
1.1 deraadt 193: example.host, and report which ones
1.6 ! aaron 194: .Nm
1.1 deraadt 195: was able to connect to.
196: .It Li "nc -v -u -z -w 3 example.host 20-30"
1.3 aaron 197: Send UDP packets to ports 20-30 of example.host, and report which ones
1.1 deraadt 198: did not respond with an ICMP packet after three seconds.
199: .It Li "nc -l -p 3000"
200: Listen on TCP port 3000, and once there is a connection, send stdin to
201: the remote host, and send data from the remote host to stdout.
202: .It Li "echo foobar | nc example.host 1000"
203: Connect to port 1000 of example.host, send the string "foobar"
204: followed by a newline, and move data from port 1000 of example.host to
205: stdout until example.host closes the connection.
206: .El
207: .Sh SEE ALSO
208: .Xr cat 1 ,
1.3 aaron 209: .Xr telnet 1
210: .Pp
211: The
1.1 deraadt 212: .Nm netcat
1.3 aaron 213: .Pa README .
1.1 deraadt 214: .Sh AUTHOR
215: *Hobbit* [hobbit@avian.org]
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