NAME
dns-sd —
Multicast DNS (mDNS) & DNS
Service Discovery (DNS-SD) Test Tool
SYNOPSIS
dns-sd -R name type
domain port [key=value
...] |
|
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 -G v4/v6/v4v6
name |
|
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,
invoking 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
machinery 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 services 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 notifications as they happen.
If you wish to perform DNS Service Discovery operations from a scripting
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
application 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 supported. In the future, registering will be
supported in any arbitrary 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 service.
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 necessarily
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 domain 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 software 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 service
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 example 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 address 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 running. 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
SEE ALSO
mDNSResponder(8)
BUGS
dns-sd bugs are tracked in Apple Radar component
"mDNSResponder".
HISTORY
The
dns-sd command first appeared in Mac OS X 10.4
(Tiger).