dns-sd(1) BSD General Commands Manual dns-sd(1)NAMEdns-sd — Multicast DNS (mDNS) & DNS Service Discovery (DNS-SD) Test Tool
SYNOPSISdns-sd-R name type domain port [key=value ...]
dns-sd-B type domain
dns-sd-L name type domain
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 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 com‐
mand 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-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 char‐
acters (including dots, spaces, slashes, colons, etc. without restric‐
tion), 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.dns-sd.org/ServiceTypes.html.
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 regis‐
tration at http://www.dns-sd.org/ServiceTypes.html.
dns-sd-B type domain
browse for instances of service type in domain.
For valid types see http://www.dns-sd.org/ServiceTypes.html as
described above. Omitting the domain or using "." means "pick a sensi‐
ble 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 happens 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.
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 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 exam‐
ple 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.
FILES
/usr/bin/dns-sd
SEE ALSOmdnsd(8)HISTORY
The dns-sd command first appeared in NetBSD 6.0, having originated in Mac
OS X 10.4 (Tiger).
NetBSD April 26, 2024 NetBSD
