dns-sd

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

Synopsis

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

dns-sd -B type domain

dns-sd -L name type domain

dns-sd -Q FQDN rrtype rrclass

dns-sd -C FQDN rrtype rrclass

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

dns-sd -E | -F | -A | -U | -N | -T | -M | -I

Description

The dns-sd command is a network diagnostic tool, much like ping(1M) or traceroute(1M). 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 can be unpredictable. Additionally, the asynchronous nature of DNS Service Discovery does not easily lend itself to script-oriented programming. 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.

Options

The following options are supported:

-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 the specified port.

name can be any arbitrary unicode text, containing any legal unicode characters (including dots, spaces, slashes, colons, and so on without any restrictions), 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, under the service types (RFC 2782) link.

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 currently means “local”.

port is a number from 0 to 65535, and is the TCP or UDP port number upon which the service is listening. Registering a service on port 0 allows an application to explicitly advertise the non-availability of a service.

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.dns-sd.org, under the service types (RFC 2782) link.

-B type domain

Browse for instances of service type in domain.

For valid types, see http://www.dns-sd.org, under the service types (RFC 2782) link. Omitting the domain name or using “.” means “pick a sensible default.”

-L name type domain

Look up and display the information necessary to contact and use the named service. This information includes 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.

In a typical application, browsing happens rarely, while lookup (or “resolving”) happens every time the service is used. For example, a user does not browse the network to pick a default printer that often, 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.

-Q FQDN rrtype rrclass

Generic query for any resource record type and class.

-C FQDN rrtype rrclass

Generic query for any resource record type and class. This option also reconfirms each result from the query. Reconfirming the record instructs mdnsd(1M) to verify the validity of the record. If the record is not valid mdnsd(1M) flushes the record from the daemon's cache and also from other mdnsd(1M) caches on the network.

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

Register (advertise) a service in the specified domain with the given name and type listening on the specified port and accessible on another host. This option should be used to advertise by proxy a service accessible on another host. The host name and IPv4 address to access the service must be specified.

-E

Discover recommended registration domains. This option returns the recommended domains to register a service. The recommended registration domains are returned by querying the name servers in resolv.conf(4).

-F

Discover recommended browsing domains. This option returns the recommended domains for browsing services. The recommended browsing domains are returned by querying the name servers in resolv.conf(4).

-A

Test registering service with Multicast DNS and test the add, update and delete operations of DNS records with Multicast DNS.

-U

Test registering service with Multicast DNS and test updating of DNS TXT records for a service registered with Multicast DNS.

-N

Test adding a large NULL record for a service registered with Multicast DNS.

-T

Test adding a large TXT record for a service registered with Multicast DNS.

-M

Test creating a registration with multiple TXT records.

-I

Test registering and then immediately updating a TXT record.

Examples

Example 1 Advertising a printing service

The following command advertises the existence of LPR printing service on port 515 on this machine, so that it will be available to DNS-SD compatible printing clients:

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

For this registration to be useful, the LPR service should be available on port 515. Advertising a service that does not exist is not very useful.

Example 2 Advertising a web page

The following command advertises a web page being served by an HTTP server on port 80 on this machine, so that it will appear on the Bonjour list in Safari and other DNS-SD compatible Web clients:

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

Example 3 Finding the advertised web pages on the local network

The following command finds the advertised web pages on the local network (the same list that Safari shows):

dns-sd -B _http._tcp

Attributes

See attributes(5) for descriptions of the following attributes:

See Also

mdnsd(1M), ping(1M), ping(1M), resolv.conf(4), attributes(5)