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1 | .\" $OpenBSD: nc.1,v 1.5 1998/09/28 06:57:35 millert Exp $ | ||
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 | ||
29 | .Dt NC 1 | ||
30 | .Os | ||
31 | .Sh NAME | ||
32 | .Nm nc | ||
33 | .Nd "arbitrary TCP and UDP connections and listens" | ||
34 | .Sh SYNOPSIS | ||
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 | ||
42 | .Op Fl p Ar source port | ||
43 | .Op Fl s Ar ip address | ||
44 | .Op Fl w Ar timeout | ||
45 | .Op Ar hostname | ||
46 | .Op Ar port[s...] | ||
47 | .Sh DESCRIPTION | ||
48 | The | ||
49 | .Nm nc | ||
50 | (or | ||
51 | .Nm netcat ) | ||
52 | utility is used for just about anything under the sun | ||
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 | ||
55 | routing. Unlike | ||
56 | .Xr telnet 1 , | ||
57 | .Nm nc | ||
58 | scripts nicely, and separates error messages onto standard error instead | ||
59 | of sending them to standard output, as | ||
60 | .Xr telnet 1 | ||
61 | does with some. | ||
62 | .Pp | ||
63 | Destination ports can be single integers, names as listed in | ||
64 | .Xr services 5 , | ||
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: | ||
69 | .Bl -bullet | ||
70 | .It | ||
71 | simple TCP proxies | ||
72 | .It | ||
73 | shell\-script based HTTP clients and servers | ||
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 | ||
87 | .Nm nc | ||
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 | ||
101 | .Nm nc | ||
102 | should listen for an incoming connection, rather than initiate a | ||
103 | connection to a remote host. Any hostname/IP address and port arguments | ||
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. | ||
111 | Each line begins with ``<'' or ``>''. ``<'' means "from the net" and ``>'' | ||
112 | means "to the net". | ||
113 | .It Fl p Ar port | ||
114 | Specifies the source port | ||
115 | .Nm nc | ||
116 | should use, subject to privilege restrictions and availability. | ||
117 | .It Fl r | ||
118 | Specifies that source and/or destination ports should be chosen semi-randomly | ||
119 | instead of sequentially within a range or in the order that the | ||
120 | system assigns. | ||
121 | .It Fl s Ar hostname/ip-address | ||
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. | ||
126 | .It Fl t | ||
127 | Causes | ||
128 | .Nm nc | ||
129 | to send RFC854 DON'T and WON'T responses to RFC854 DO | ||
130 | and WILL requests. This makes it possible to use | ||
131 | .Nm nc | ||
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 | ||
135 | Use UDP instead of TCP. | ||
136 | On most platforms, | ||
137 | .Nm nc | ||
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 | ||
143 | .Nm nc | ||
144 | to display connection information. Using | ||
145 | .Fl v | ||
146 | more than once will cause | ||
147 | .Nm nc | ||
148 | to become even more verbose. | ||
149 | .It Fl w Ar timeout | ||
150 | Specifies the number of seconds | ||
151 | .Nm nc | ||
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 | ||
158 | .Nm nc | ||
159 | should just scan for listening | ||
160 | daemons, without sending any data to them. Diagnostic messages about refused | ||
161 | connections will not be | ||
162 | displayed unless | ||
163 | .Fl v | ||
164 | is specified twice. | ||
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" | ||
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 cat 1 , | ||
209 | .Xr telnet 1 | ||
210 | .Pp | ||
211 | The | ||
212 | .Nm netcat | ||
213 | .Pa README . | ||
214 | .Sh AUTHOR | ||
215 | *Hobbit* [hobbit@avian.org] | ||