Annotation of src/usr.bin/nc/nc.1, Revision 1.18
1.18 ! krw 1: .\" $OpenBSD: nc.1,v 1.17 2001/08/30 13:21:50 krw Exp $
1.1 deraadt 2: .\"
3: .\" Copyright (c) 1996 David Sacerdote
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1.13 ericj 28: .Dd June 25, 2001
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
1.13 ericj 36: .Op Fl 46hklnrtuvz
1.1 deraadt 37: .Op Fl i Ar interval
1.6 aaron 38: .Op Fl p Ar source port
1.13 ericj 39: .Op Fl s Ar source ip address
1.6 aaron 40: .Op Fl w Ar timeout
1.1 deraadt 41: .Op Ar hostname
1.13 ericj 42: .Op Ar port[s]
1.1 deraadt 43: .Sh DESCRIPTION
44: The
1.6 aaron 45: .Nm
1.1 deraadt 46: (or
47: .Nm netcat )
1.13 ericj 48: utility is used for just about anything under the sun involving TCP
49: or UDP.
50: It can open TCP connections, send UDP packets, listen on arbitrary
51: TCP and UDP ports, do port scanning, and deal with both IPv4 and
52: IPv6.
1.7 aaron 53: Unlike
1.1 deraadt 54: .Xr telnet 1 ,
1.6 aaron 55: .Nm
1.1 deraadt 56: scripts nicely, and separates error messages onto standard error instead
1.6 aaron 57: of sending them to standard output, as
1.13 ericj 58: .Xr telnet 1 ,
1.6 aaron 59: does with some.
1.1 deraadt 60: .Pp
1.13 ericj 61: Destination ports can be single integers or ranges.
62: Ranges are in the form nn-mm.
1.1 deraadt 63: .Pp
64: Common uses include:
1.7 aaron 65: .Pp
66: .Bl -bullet -offset indent -compact
1.1 deraadt 67: .It
1.3 aaron 68: simple TCP proxies
1.1 deraadt 69: .It
1.3 aaron 70: shell\-script based HTTP clients and servers
1.1 deraadt 71: .It
1.13 ericj 72: network daemon testing
1.1 deraadt 73: .It
74: and much, much more
75: .El
76: .Pp
77: The options are as follows:
78: .Bl -tag -width Ds
1.13 ericj 79: .It Fl 4
80: Forces
81: .Nm
82: to use IPv4 addresses only.
83: .It Fl 6
84: Forces
85: .Nm
86: to use IPv6 addresses only.
87: .It Fl h
88: Prints out
89: .Nm
90: help.
91: .It Fl i Ar interval
1.1 deraadt 92: Specifies a delay time interval between lines of text sent and received.
93: Also causes a delay time between connections to multiple ports.
1.13 ericj 94: .It Fl k
95: Forces
96: .Nm
1.14 jasoni 97: to stay listening for another connection after it's current connection
1.13 ericj 98: is completed.
1.1 deraadt 99: .It Fl l
1.13 ericj 100: Used to specify that
1.6 aaron 101: .Nm
1.13 ericj 102: should listen for an incoming connection rather than initiate a
1.7 aaron 103: connection to a remote host.
1.1 deraadt 104: .It Fl n
1.13 ericj 105: Do not do any DNS or service lookups on any specified addresses or
106: hostnames, or ports.
1.1 deraadt 107: .It Fl p Ar port
108: Specifies the source port
1.6 aaron 109: .Nm
1.1 deraadt 110: should use, subject to privilege restrictions and availability.
111: .It Fl r
1.13 ericj 112: Specifies that source and/or destination ports should be chosen randomly
113: instead of sequentially within a range or in the order that the system
114: assigns.
115: .It Fl s Ar hostname/ip address
1.3 aaron 116: Specifies the IP of the interface which is used to send the packets.
1.1 deraadt 117: .It Fl t
118: Causes
1.6 aaron 119: .Nm
1.13 ericj 120: to send RFC854 DON'T and WON'T responses to RFC854 DO and WILL requests.
1.7 aaron 121: This makes it possible to use
1.6 aaron 122: .Nm
1.7 aaron 123: to script telnet sessions.
1.1 deraadt 124: .It Fl u
1.13 ericj 125: Use UDP instead of the default option of TCP.
1.1 deraadt 126: .It Fl v
1.13 ericj 127: Have
1.6 aaron 128: .Nm
1.13 ericj 129: give more verbose output.
1.1 deraadt 130: .It Fl z
131: Specifies that
1.6 aaron 132: .Nm
1.13 ericj 133: should just scan for listening daemons, without sending any data to them.
1.8 aaron 134: .El
1.1 deraadt 135: .Sh EXAMPLES
136: .Bl -tag -width x
1.13 ericj 137: .It Li "nc hostname 42"
138: Open a TCP connection to port 42 of hostname.
139: .It Li "nc -p 31337 hostname 42"
140: Open a TCP connection to port 42 of hostname, and use port 31337 as
141: the source port.
142: .It Li "nc -w 5 hostname 42"
143: Open a TCP connection to port 42 of hostname, and timeout after
1.1 deraadt 144: five seconds while attempting to connect.
1.13 ericj 145: .It Li "nc -u hostname 53"
146: Open a UDP connection to port 53 of hostname.
1.1 deraadt 147: .It Li "nc -s 10.1.2.3 example.host 42"
1.3 aaron 148: Open a TCP connection to port 42 of example.host using 10.1.2.3 as the
149: IP for the local end of the connection.
1.13 ericj 150: .It Li "nc -v hostname 42"
151: Open a TCP connection to port 42 of hostname, displaying some
1.1 deraadt 152: diagnostic messages on stderr.
1.13 ericj 153: .It Li "nc -v -v hostname 42"
154: Open a TCP connection to port 42 of hostname, displaying all
1.1 deraadt 155: diagnostic messages on stderr.
1.13 ericj 156: .It Li "nc -v -z hostname 20-30"
1.3 aaron 157: Attempt to open TCP connections to ports 20 through 30 of
1.17 krw 158: hostname, and report which ones
1.6 aaron 159: .Nm
1.1 deraadt 160: was able to connect to.
1.13 ericj 161: .It Li "nc -v -u -z -w 3 hostname 20-30"
1.3 aaron 162: Send UDP packets to ports 20-30 of example.host, and report which ones
1.1 deraadt 163: did not respond with an ICMP packet after three seconds.
1.16 ericj 164: .It Li "nc -l 3000"
1.1 deraadt 165: Listen on TCP port 3000, and once there is a connection, send stdin to
166: the remote host, and send data from the remote host to stdout.
1.13 ericj 167: .It Li "echo foobar | nc hostname 1000"
168: Connect to port 1000 of hostname, send the string "foobar"
169: followed by a newline, and move data from port 1000 of hostname to
170: stdout until hostname closes the connection.
1.1 deraadt 171: .El
172: .Sh SEE ALSO
173: .Xr cat 1 ,
1.3 aaron 174: .Xr telnet 1
1.15 smart 175: .Sh AUTHORS
176: Original implementation by *Hobbit*
177: .Aq hobbit@avian.org .
178: .Pp
179: Rewritten with IPv6 support by Eric Jackson
180: .Aq ericj@monkey.org .
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