mDNSShared/mDNS.1

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  22 .\" $Log: mDNS.1,v $
  23 .\" Revision 1.7  2005/02/16 02:29:32  cheshire
  24 .\" Update terminology
  25 .\"
  26 .\" Revision 1.6  2005/02/10 22:35:28  cheshire
  27 .\" <rdar://problem/3727944> Update name
  28 .\"
  29 .\" Revision 1.5  2004/09/24 18:33:05  cheshire
  30 .\" <rdar://problem/3561780> Update man pages to clarify that mDNS and dns-sd are not intended for script use
  31 .\"
  32 .\" Revision 1.4  2004/09/22 22:18:48  cheshire
  33 .\" Update man page to cross-reference new dns-sd man page
  34 .\"
  35 .\" Revision 1.3  2004/05/19 00:31:28  cheshire
  36 .\" Add missing "name type domain" for -L option
  37 .\"
  38 .\" Revision 1.2  2004/05/18 18:58:29  cheshire
  39 .\" Refinements from Soren Spies
  40 .\"
  41 .\" Revision 1.1  2004/04/22 02:52:53  cheshire
  42 .\" <rdar://problem/3597463>: mDNSResponder missing man pages: mDNS
  43 .\"
  44 .\"
  45 .\"
  46 .Dd April 2004              \" Date
  47 .Dt mDNS 1                  \" Document Title
  48 .Os Darwin                  \" Operating System
  49 .\"
  50 .Sh NAME
  51 .Nm mDNS
  52 .Nd Multicast DNS (mDNS) & DNS Service Discovery (DNS-SD) Test Tool \" For whatis
  53 .\"
  54 .Sh SYNOPSIS
  55 .Nm Fl R Ar name type domain port Op Ar key=value ...
  56 .Pp
  57 .Nm Fl B Ar      type domain
  58 .Pp
  59 .Nm Fl L Ar name type domain
  60 .\"
  61 .Sh DESCRIPTION
  62 The
  63 .Nm
  64 command is a network diagnostic tool, much like
  65 .Xr ping 8
  66 or
  67 .Xr traceroute 8 .
  68 However, unlike those tools, most of its functionality is not implemented in the
  69 .Nm
  70 executable itself, but in library code that is available to any application.
  71 The library API that
  72 .Nm
  73 uses is documented in
  74 .Pa /usr/include/DNSServiceDiscovery/DNSServiceDiscovery.h .
  75 Note that this Mach-based API, first introduced in Mac OS X 10.2,
  76 is now deprecated in favour of the newer
  77 .Pa /usr/include/dns_sd.h
  78 API, which is built on Unix Domain Sockets and is supported on
  79 multiple platforms.
  80 The command-line tool to exercise the cross-platform
  81 .Pa dns_sd.h
  82 API is
  83 .Xr dns-sd 1 .
  84 .Pp
  85 The
  86 .Nm
  87 command is primarily intended for interactive use.
  88 Because its command-line arguments and output format are subject to change,
  89 invoking it from a shell script will generally be fragile. Additionally,
  90 the asynchronous nature of DNS Service Discovery does
  91 not lend itself easily to script-oriented programming. For example,
  92 calls like "browse" never complete; the action of performing a "browse"
  93 sets in motion machinery to notify the client whenever instances of
  94 that service type appear or disappear from the network. These
  95 notifications continue to be delivered indefinitely, for minutes,
  96 hours, or even days, as services come and go, until the client
  97 explicitly terminates the call. This style of asynchronous interaction
  98 works best with applications that are either multi-threaded, or use a
  99 main event-handling loop to receive keystrokes, network data, and other
 100 asynchronous event notifications as they happen.
 101 .br
 102 If you wish to perform DNS Service Discovery operations from a
 103 scripting language, then the best way to do this is not to execute the
 104 .Nm
 105 command and then attempt to decipher the textual output, but instead to
 106 directly call the DNS-SD APIs using a binding for your chosen language.
 107 .br
 108 For example, if you are programming in Ruby, then you can
 109 directly call DNS-SD APIs using the dnssd package documented at
 110 .Pa <http://rubyforge.org/projects/dnssd/> .
 111 .br
 112 Similar bindings for other languages are also in development.
 113 .Pp
 114 .Bl -tag -width R
 115 .It Nm Fl R Ar name type domain port Op Ar key=value ...
 116 register (advertise) a service in the specified
 117 .Ar domain
 118 with the given
 119 .Ar name
 120 and
 121 .Ar type
 122 as listening (on the current machine) on
 123 .Ar port.
 124 .Pp
 125 .Ar name
 126 can be arbitrary unicode text, containing any legal unicode characters
 127 (including dots, spaces, slashes, colons, etc. without restriction),
 128 up to 63 UTF-8 bytes long.
 129 .Ar type
 130 must be of the form "_app-proto._tcp" or "_app-proto._udp", where
 131 "app-proto" is an application protocol name registered at
 132 .Pa http://www.dns-sd.org/ServiceTypes.html .
 133 .Pp
 134 .Ar domain
 135 is the domain in which to register the service.
 136 In current implementations, only the local multicast domain "local" is
 137 supported. In the future, registering will be supported in any arbitrary
 138 domain that has a working DNS Update server [RFC 2136]. The
 139 .Ar domain
 140 "." is a synonym for "pick a sensible default" which today
 141 means "local".
 142 .Pp
 143 .Ar port
 144 is a number from 0 to 65535, and is the TCP or UDP port number upon
 145 which the service is listening.
 146 .Pp
 147 Additional attributes of the service may optionally be described by
 148 key/value pairs, which are stored in the advertised service's DNS TXT
 149 record. Allowable keys and values are listed with the service
 150 registration at
 151 .Pa http://www.dns-sd.org/ServiceTypes.html .
 152 .It Nm Fl B Ar type domain
 153 browse for instances of service
 154 .Ar type
 155 in
 156 .Ar domain .
 157 .Pp
 158 For valid
 159 .Ar type Ns s
 160 see
 161 .Pa http://www.dns-sd.org/ServiceTypes.html
 162 as described above. Omitting the
 163 .Ar domain
 164 or using "." means "pick a sensible default."
 165 .It Nm Fl L Ar name type domain
 166 look up and display the information necessary to contact and use the
 167 named service: the hostname of the machine where that service is
 168 available, the port number on which the service is listening, and (if
 169 present) TXT record attributes describing properties of the service.
 170 .Pp
 171 Note that in a typical application, browsing happens rarely, while lookup
 172 (or "resolving") happens every time the service is used. For example, a
 173 user browses the network to pick a default printer fairly rarely, but once
 174 a default printer has been picked, that named service is resolved to its
 175 current IP address and port number every time the user presses Cmd-P to
 176 print.
 177 .El
 178 .Sh EXAMPLES
 179 .Pp
 180 To advertise the existence of LPR printing service on port 515 on this
 181 machine, such that it will be discovered by the Mac OS X printing software
 182 and other DNS-SD compatible printing clients, use:
 183 .Pp
 184 .Dl Nm Fl R Ns \ \&"My Test\&" _printer._tcp. \&. 515 pdl=application/postscript
 185 .Pp
 186 For this registration to be useful, you need to actually have LPR service
 187 available on port 515. Advertising a service that does not exist is not
 188 very useful, and will be confusing and annoying to other people on the
 189 network.
 190 .Pp
 191 Similarly, to advertise a web page being served by an HTTP
 192 server on port 80 on this machine, such that it will show up in the
 193 Bonjour list in Safari and other DNS-SD compatible Web clients, use:
 194 .Pp
 195 .Dl Nm Fl R Ns \ \&"My Test\&" _http._tcp \&. 80 path=/path-to-page.html
 196 .Pp
 197 To find the advertised web pages on the local network (the same list that
 198 Safari shows), use:
 199 .Pp
 200 .Dl Nm Fl B Ns \ _http._tcp
 201 .Pp
 202 While that command is running, in another window, try the
 203 .Nm Fl R
 204 example given above to advertise a web page, and you should see the
 205 "Add" event reported to the
 206 .Nm Fl B
 207 window. Now press Ctrl-C in the
 208 .Nm Fl R
 209 window and you should see the "Remove" event reported to the
 210 .Nm Fl B
 211 window.
 212 .Pp
 213 .Sh FILES
 214 .Pa /usr/bin/mDNS \" Pathname
 215 .\"
 216 .Sh SEE ALSO
 217 .Xr dns-sd 1
 218 .Xr mDNSResponder 8
 219 .\"
 220 .Sh BUGS
 221 .Nm
 222 bugs are tracked in Apple Radar component "mDNSResponder".
 223 .\"
 224 .Sh HISTORY
 225 The
 226 .Nm
 227 command first appeared in Mac OS X 10.3 (Panther).