Annotation of src/usr.bin/nc/nc.1, Revision 1.12
1.12 ! millert 1: .\" $OpenBSD: nc.1,v 1.11 2000/09/26 01:41:44 ericj 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,
21: .\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
22: .\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
23: .\" DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
24: .\" THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
25: .\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
26: .\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
27: .\"
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
1.9 aaron 36: .Op Fl lnrtuvz
1.1 deraadt 37: .Op Fl g Ar intermediates
38: .Op Fl G Ar hopcount
39: .Op Fl i Ar interval
40: .Op Fl o Ar filename
1.6 aaron 41: .Op Fl p Ar source port
1.1 deraadt 42: .Op Fl s Ar ip address
1.6 aaron 43: .Op Fl w Ar timeout
1.1 deraadt 44: .Op Ar hostname
45: .Op Ar port[s...]
46: .Sh DESCRIPTION
47: The
1.6 aaron 48: .Nm
1.1 deraadt 49: (or
50: .Nm netcat )
51: utility is used for just about anything under the sun
1.7 aaron 52: involving TCP or UDP.
53: It can open TCP connections, send UDP packets,
1.3 aaron 54: listen on arbitrary TCP and UDP ports, do port scanning, and source
1.7 aaron 55: routing.
56: Unlike
1.1 deraadt 57: .Xr telnet 1 ,
1.6 aaron 58: .Nm
1.1 deraadt 59: scripts nicely, and separates error messages onto standard error instead
1.6 aaron 60: of sending them to standard output, as
61: .Xr telnet 1
62: does with some.
1.1 deraadt 63: .Pp
64: Destination ports can be single integers, names as listed in
1.5 millert 65: .Xr services 5 ,
1.7 aaron 66: or ranges.
67: Ranges are in the form nn-mm, and several separate ports and/or
1.1 deraadt 68: ranges may be specified on the command line.
69: .Pp
70: Common uses include:
1.7 aaron 71: .Pp
72: .Bl -bullet -offset indent -compact
1.1 deraadt 73: .It
1.3 aaron 74: simple TCP proxies
1.1 deraadt 75: .It
1.3 aaron 76: shell\-script based HTTP clients and servers
1.1 deraadt 77: .It
78: network daemon testing
79: .It
80: source routing based connectivity testing
81: .It
82: and much, much more
83: .El
84: .Pp
85: The options are as follows:
86: .Bl -tag -width Ds
87: .It Fl g Ar intermediate-host
1.7 aaron 88: Specifies a hop along a loose source routed path.
89: Can be used more than once to build a chain of hop points.
1.1 deraadt 90: .It Fl G Ar pointer
1.7 aaron 91: Positions the
92: .Dq hop counter
93: within the list of machines in the path of a source routed packet.
94: Must be a multiple of 4.
1.1 deraadt 95: .It Fl i Ar seconds
96: Specifies a delay time interval between lines of text sent and received.
97: Also causes a delay time between connections to multiple ports.
98: .It Fl l
99: Is used to specify that
1.6 aaron 100: .Nm
1.1 deraadt 101: should listen for an incoming connection, rather than initiate a
1.7 aaron 102: connection to a remote host.
103: 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.
1.7 aaron 111: Each line begins with
112: .Ql <
113: or
114: .Ql > .
115: .Ql <
116: means
117: .Dq from the net
118: and
119: .Ql >
120: means
121: .Dq to the net .
1.1 deraadt 122: .It Fl p Ar port
123: Specifies the source port
1.6 aaron 124: .Nm
1.1 deraadt 125: should use, subject to privilege restrictions and availability.
126: .It Fl r
1.3 aaron 127: Specifies that source and/or destination ports should be chosen semi-randomly
1.1 deraadt 128: instead of sequentially within a range or in the order that the
129: system assigns.
130: .It Fl s Ar hostname/ip-address
1.3 aaron 131: Specifies the IP of the interface which is used to send the packets.
132: On some platforms, this can be used for UDP spoofing by using
133: .Xr ifconfig 8
134: to bring up a dummy interface with the desired source IP address.
1.1 deraadt 135: .It Fl t
136: Causes
1.6 aaron 137: .Nm
1.1 deraadt 138: to send RFC854 DON'T and WON'T responses to RFC854 DO
1.7 aaron 139: and WILL requests.
140: This makes it possible to use
1.6 aaron 141: .Nm
1.7 aaron 142: to script telnet sessions.
143: The presence of this option can be
1.1 deraadt 144: enabled or disabled as a compile-time option.
145: .It Fl u
1.6 aaron 146: Use UDP instead of TCP.
1.1 deraadt 147: On most platforms,
1.6 aaron 148: .Nm
1.1 deraadt 149: will behave as if a connection is established until it receives an
150: ICMP packet indicating that there is no program listening to what it
151: sends.
152: .It Fl v
1.7 aaron 153: Verbose.
154: Cause
1.6 aaron 155: .Nm
1.7 aaron 156: to display connection information.
157: Using
1.3 aaron 158: .Fl v
1.1 deraadt 159: more than once will cause
1.6 aaron 160: .Nm
1.1 deraadt 161: to become even more verbose.
162: .It Fl w Ar timeout
163: Specifies the number of seconds
1.6 aaron 164: .Nm
1.1 deraadt 165: should wait before deciding that
166: an attempt to establish a connection is hopeless.
167: Also used to specify how long to wait for more network data after standard
168: input closes.
169: .It Fl z
170: Specifies that
1.6 aaron 171: .Nm
1.1 deraadt 172: should just scan for listening
1.7 aaron 173: daemons, without sending any data to them.
1.10 ian 174: Diagnostic messages about refused connections will not be displayed unless
1.3 aaron 175: .Fl v
176: is specified twice.
1.8 aaron 177: .El
1.1 deraadt 178: .Sh EXAMPLES
179: .Bl -tag -width x
180: .It Li "nc"
181: Wait for the user to type what would normally be command-line
1.10 ian 182: arguments on stdin.
1.1 deraadt 183: .It Li "nc example.host 42"
1.7 aaron 184: Open a TCP connection to port 42 of example.host.
185: If the connection
1.1 deraadt 186: fails, do not display any error messages, but simply exit.
187: .It Li "nc -p 31337 example.host 42"
188: Open a TCP connection to port 42 of example.host, and use port 31337
189: as the source port.
190: .It Li "nc -w 5 example.host 42"
1.3 aaron 191: Open a TCP connection to port 42 of example.host, and time out after
1.1 deraadt 192: five seconds while attempting to connect.
193: .It Li "nc -u example.host 53"
194: Send any data from stdin
195: to UDP port 53 of example.host, and display any data returned.
196: .It Li "nc -s 10.1.2.3 example.host 42"
1.3 aaron 197: Open a TCP connection to port 42 of example.host using 10.1.2.3 as the
198: IP for the local end of the connection.
1.1 deraadt 199: .It Li "nc -v example.host 42"
1.3 aaron 200: Open a TCP connection to port 42 of example.host, displaying some
1.1 deraadt 201: diagnostic messages on stderr.
202: .It Li "nc -v -v example.host 42"
1.3 aaron 203: Open a TCP connection to port 42 of example.host, displaying all
1.1 deraadt 204: diagnostic messages on stderr.
205: .It Li "nc -v -z example.host 20-30"
1.3 aaron 206: Attempt to open TCP connections to ports 20 through 30 of
1.1 deraadt 207: example.host, and report which ones
1.6 aaron 208: .Nm
1.1 deraadt 209: was able to connect to.
210: .It Li "nc -v -u -z -w 3 example.host 20-30"
1.3 aaron 211: Send UDP packets to ports 20-30 of example.host, and report which ones
1.1 deraadt 212: did not respond with an ICMP packet after three seconds.
213: .It Li "nc -l -p 3000"
214: Listen on TCP port 3000, and once there is a connection, send stdin to
215: the remote host, and send data from the remote host to stdout.
216: .It Li "echo foobar | nc example.host 1000"
217: Connect to port 1000 of example.host, send the string "foobar"
218: followed by a newline, and move data from port 1000 of example.host to
219: stdout until example.host closes the connection.
220: .El
221: .Sh SEE ALSO
222: .Xr cat 1 ,
1.3 aaron 223: .Xr telnet 1
224: .Pp
225: The
1.1 deraadt 226: .Nm netcat
1.3 aaron 227: .Pa README .
1.1 deraadt 228: .Sh AUTHOR
229: *Hobbit* [hobbit@avian.org]
![[BACK]](/icons/back.gif){kind=icon}
Return to nc.1 CVS log ![[TXT]](/icons/text.gif){kind=icon}
![[DIR]](/icons/dir.gif){kind=icon}
Up to [local] / src / usr.bin / nc