DNS-SD(8) | Maintenance Commands and Procedures | DNS-SD(8) |
dns-sd
— Multicast
DNS (mDNS) & DNS Service Discovery (DNS-SD) Test Tool
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 ] |
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
dns-sd
-F
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
...]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 domainFor 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 domainNote 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 ...]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 rrclassdns-sd
-Z
type domaindns-sd
-G
v4/v6/v4v6 namedns-sd
-V
/usr/bin/dns-sd
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
January 28, 2016 | illumos |