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dns-sd(1) General Commands Manual dns-sd(1)

NAME
dns-sd -- Multicast DNS (mDNS) & DNS Service Discovery (DNS-SD) Test
Tool

SYNOPSIS
dns-sd -E

dns-sd -F

dns-sd -R name type domain port [key=value ...]

dns-sd -B type domain

dns-sd -L name type domain

dns-sd -P name type domain port host IP [key=value ...]

dns-sd -q name rrtype rrclass

dns-sd -Z type domain

dns-sd -G v4/v6/v4v6 name

dns-sd -V

DESCRIPTION
The dns-sd command is a network diagnostic tool, much like ping(8) or
traceroute(8). However, unlike those tools, most of its functionality
is not implemented in the dns-sd executable itself, but in library code
that is available to any application. The library API that dns-sd uses
is documented in /usr/include/dns_sd.h. The dns-sd command replaces
the older mDNS command.

The dns-sd command is primarily intended for interactive use. Because
its command-line arguments and output format are subject to change, in-
voking it from a shell script will generally be fragile. Additionally,
the asynchronous nature of DNS Service Discovery does not lend itself
easily to script-oriented programming. For example, calls like "browse"
never complete; the action of performing a "browse" sets in motion ma-
chinery to notify the client whenever instances of that service type
appear or disappear from the network. These notifications continue to
be delivered indefinitely, for minutes, hours, or even days, as ser-
vices come and go, until the client explicitly terminates the call.
This style of asynchronous interaction works best with applications
that are either multi-threaded, or use a main event-handling loop to
receive keystrokes, network data, and other asynchronous event notifi-
cations as they happen.
If you wish to perform DNS Service Discovery operations from a script-
ing language, then the best way to do this is not to execute the dns-sd
command and then attempt to decipher the textual output, but instead to
directly call the DNS-SD APIs using a binding for your chosen language.
For example, if you are programming in Ruby, then you can directly call
DNS-SD APIs using the dnssd package documented at
<http://rubyforge.org/projects/dnssd/>.
Similar bindings for other languages are also in development.

dns-sd -E
return a list of domains recommended for registering(advertising)
services.

dns-sd -F
return a list of domains recommended for browsing services.

Normally, on your home network, the only domain you are likely to
see is "local". However if your network administrator has created
Domain Enumeration records, then you may also see other recommended
domains for registering and browsing.

dns-sd -R name type domain port [key=value ...]
register (advertise) a service in the specified domain with the
given name and type as listening (on the current machine) on port.

name can be arbitrary unicode text, containing any legal unicode
characters (including dots, spaces, slashes, colons, etc. without
restriction), up to 63 UTF-8 bytes long. type must be of the form
"_app-proto._tcp" or "_app-proto._udp", where "app-proto" is an ap-
plication protocol name registered at
http://www.iana.org/assignments/service-names-port-numbers/service-names-port-numbers.xml.

domain is the domain in which to register the service. In current
implementations, only the local multicast domain "local" is sup-
ported. In the future, registering will be supported in any arbi-
trary domain that has a working DNS Update server [RFC 2136]. The
domain "." is a synonym for "pick a sensible default" which today
means "local".

port is a number from 0 to 65535, and is the TCP or UDP port number
upon which the service is listening.

Additional attributes of the service may optionally be described by
key/value pairs, which are stored in the advertised service's DNS
TXT record. Allowable keys and values are listed with the service
registration at
http://www.iana.org/assignments/service-names-port-numbers/service-names-port-numbers.xml.

dns-sd -B type domain
browse for instances of service type in domain.

For valid types see
http://www.iana.org/assignments/service-names-port-numbers/service-names-port-numbers.xml.
as described above. Omitting the domain or using "." means "pick a
sensible default."

dns-sd -L name type domain
look up and display the information necessary to contact and use the
named service: the hostname of the machine where that service is
available, the port number on which the service is listening, and
(if present) TXT record attributes describing properties of the ser-
vice.

Note that in a typical application, browsing may only happen rarely,
while lookup (or "resolving") happens every time the service is
used. For example, a user browses the network to pick a default
printer fairly rarely, but once a default printer has been picked,
that named service is resolved to its current IP address and port
number every time the user presses Cmd-P to print.

dns-sd -P name type domain port host IP [key=value ...]
create a proxy advertisement for a service running on(offered by)
some other machine. The two new options are Host, a name for the
device and IP, the address of it.

The service for which you create a proxy advertisement does not nec-
essarily have to be on your local network. You can set up a local
proxy for a website on the Internet.

dns-sd -q name rrtype rrclass
look up any DNS name, resource record type, and resource record
class, not necessarily DNS-SD names and record types. If rrtype is
not specified, it queries for the IPv4 address of the name, if
rrclass is not specified, IN class is assumed. If the name is not a
fully qualified domain name, then search domains may be appended.

dns-sd -Z type domain
browse for service instances and display output in zone file format.

dns-sd -G v4/v6/v4v6 name
look up the IP address information of the name. If v4 is specified,
the IPv4 address of the name is looked up, if v6 is specified the
IPv6 address is looked up. If v4v6 is specified both the IPv4 and
IPv6 address is looked up. If the name is not a fully qualified do-
main name, then search domains may be appended.

dns-sd -V
return the version of the currently running daemon/system service.

EXAMPLES
To advertise the existence of LPR printing service on port 515 on this
machine, such that it will be discovered by the Mac OS X printing soft-
ware and other DNS-SD compatible printing clients, use:

dns-sd -R "My Test" _printer._tcp. . 515
pdl=application/postscript

For this registration to be useful, you need to actually have LPR ser-
vice available on port 515. Advertising a service that does not exist
is not very useful, and will be confusing and annoying to other people
on the network.

Similarly, to advertise a web page being served by an HTTP server on
port 80 on this machine, such that it will show up in the Bonjour list
in Safari and other DNS-SD compatible Web clients, use:

dns-sd -R "My Test" _http._tcp . 80 path=/path-to-page.html

To find the advertised web pages on the local network (the same list
that Safari shows), use:

dns-sd -B _http._tcp

While that command is running, in another window, try the dns-sd -R ex-
ample given above to advertise a web page, and you should see the "Add"
event reported to the dns-sd -B window. Now press Ctrl-C in the dns-sd
-R window and you should see the "Remove" event reported to the dns-sd
-B window.

In the example below, the www.apple.com web page is advertised as a
service called "apple", running on a target host called apple.local,
which resolves to 17.149.160.49.

dns-sd -P apple _http._tcp "" 80 apple.local 17.149.160.49

The Bonjour menu in the Safari web browser will now show "apple". The
same IP address can be reached by entering apple.local in the web
browser. In either case, the request will be resolved to the IP ad-
dress and browser will show contents associated with www.apple.com.

If a client wants to be notified of changes in server state, it can
initiate a query for the service's particular record and leave it run-
ning. For example, to monitor the status of an iChat user you can use:

dns-sd -q someone@ex1._presence._tcp.local txt

Everytime status of that user(someone) changes, you will see a new TXT
record result reported.

You can also query for a unicast name like www.apple.com and monitor
its status.

dns-sd -q www.apple.com

FILES
/usr/bin/dns-sd

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