mDNSShared/mDNS.1

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