Annotation of src/usr.bin/nc/nc.1, Revision 1.2
1.2 ! deraadt 1: .\" $OpenBSD: nc.1,v 1.1 1996/09/05 08:55:32 deraadt 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
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11: .\" 2. Redistributions in binary form must reproduce the above copyright
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17: .\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
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28: .Dd August 1, 1996
29: .Dt nc 1
30: .Sh NAME
31: .Os
32: .Nm nc
33: .Nd
34: Arbitrary tcp and udp connections and listens.
35: .Pp
1.2 ! deraadt 36: .Sh SYNOPSIS
1.1 deraadt 37: .Nm nc
38: .Op Fl e Ar command
39: .Op Fl g Ar intermediates
40: .Op Fl G Ar hopcount
41: .Op Fl i Ar interval
42: .Op Fl lnrtuvz
43: .Op Fl o Ar filename
44: .Op Fl p Ar source port
45: .Op Fl s Ar ip address
46: .Op Fl w Ar timeout
47: .Op Ar hostname
48: .Op Ar port[s...]
49: .Pp
50: .Sh DESCRIPTION
51: The
52: .Nm nc
53: (or
54: .Nm netcat )
55: utility is used for just about anything under the sun
56: involving TCP or UDP. It can open tcp connections, send udp packets,
57: listen on arbitrary tcp and udp ports, do port scanning, and source
58: routing. Unlike
59: .Xr telnet 1 ,
60: .Nm nc
61: scripts nicely, and separates error messages onto standard error instead
62: of sending them to standard output, as
63: .Xr telnet 1
64: does with some.
65: .Pp
66: Destination ports can be single integers, names as listed in
67: .Xr /etc/services 5 ,
68: or ranges. Ranges are in the form nn-mm, and several separate ports and/or
69: ranges may be specified on the command line.
70: .Pp
71: Common uses include:
72: .Bl -bullet
73: .It
74: simple tcp proxies
75: .It
76: shell\-script based http clients and servers
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 e Ar command
88: Execute the specified command, using data from the network for stdin,
89: and sending stdout and stderr to the network. This option is only present if
90: .Nm nc
91: was compiled with the GAPING_SECURITY_HOLE compile time option, since it
92: allows users to make arbitrary programs available to anyone on the network.
93: .It Fl g Ar intermediate-host
94: Specifies a hop along a loose source routed path. Can be used more than
95: once to build a chain of hop points.
96: .It Fl G Ar pointer
97: Positions the "hop counter" within the list of machines in the path of
98: a source routed packet. Must be a multiple of 4.
99: .It Fl i Ar seconds
100: Specifies a delay time interval between lines of text sent and received.
101: Also causes a delay time between connections to multiple ports.
102: .It Fl l
103: Is used to specify that
104: .Nm nc
105: should listen for an incoming connection, rather than initiate a
106: connection to a remote host. Any hostname/ip address and port arguments
107: restrict the source of inbound connections to only that address and
108: source port.
109: .It Fl n
110: Do not do DNS lookups on any of the specified addresses or hostnames, or
111: names of port numbers from /etc/services.
112: .It Fl o Ar filename
113: Create a hexadecimal log of data transferred in the specified file.
114: Each line begins with < or >. < means "from the net" and > means
115: "to the net."
116: .It Fl p Ar port
117: Specifies the source port
118: .Nm nc
119: should use, subject to privilege restrictions and availability.
120: .It Fl r
121: Specified that source and/or destination ports should be chosen semi-randomly
122: instead of sequentially within a range or in the order that the
123: system assigns.
124: .It Fl s Ar hostname/ip-address
125: Specifies the ip of the interface which is used to send the packets.
126: On some platforms, this can be used for udp spoofing by using ifconfig
127: to bring up a dummy interface with the desired source ip address.
128: .It Fl t
129: Causes
130: .Nm nc
131: to send RFC854 DON'T and WON'T responses to RFC854 DO
132: and WILL requests. This makes it possible to use
133: .Nm nc
134: to script telnet sessions. The presence of this option can be
135: enabled or disabled as a compile-time option.
136: .It Fl u
137: Use UDP instead of TCP.
138: On most platforms,
139: .Nm nc
140: will behave as if a connection is established until it receives an
141: ICMP packet indicating that there is no program listening to what it
142: sends.
143: .It Fl v
144: Verbose. Cause
145: .Nm nc
146: to display connection information. Using \-v
147: more than once will cause
148: .Nm nc
149: to become even more verbose.
150: .It Fl w Ar timeout
151: Specifies the number of seconds
152: .Nm nc
153: should wait before deciding that
154: an attempt to establish a connection is hopeless.
155: Also used to specify how long to wait for more network data after standard
156: input closes.
157: .It Fl z
158: Specifies that
159: .Nm nc
160: should just scan for listening
161: daemons, without sending any data to them. Diagnostic messages about refused
162: connections will not be
163: displayed unless \-v is specified twice.
164: .Sh EXAMPLES
165: .Pp
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"
177: Open a tcp connection to port 42 of example.host, and time out after
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"
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.
185: .It Li "nc -v example.host 42"
186: Open a tcp connection to port 42 of example.host, displaying some
187: diagnostic messages on stderr.
188: .It Li "nc -v -v example.host 42"
189: Open a tcp connection to port 42 of example.host, displaying all
190: diagnostic messages on stderr.
191: .It Li "nc -v -z example.host 20-30"
192: Attempt to open tcp connections to ports 20 through 30 of
193: example.host, and report which ones
194: .Nm nc
195: was able to connect to.
196: .It Li "nc -v -u -z -w 3 example.host 20-30"
197: Send udp packets to ports 20-30 of example.host, and report which ones
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 telnet 1 ,
209: .Xr cat 1 ,
210: and the
211: .Nm netcat
212: .Pa README
213: .Sh AUTHOR
214: *Hobbit* [hobbit@avian.org]
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