KDNSSD 5.109.0
Public Types | Signals | Public Member Functions | Static Public Member Functions | Protected Member Functions | List of all members
KDNSSD::ServiceBrowser

Browses for network services advertised over DNS-SD. More...

#include <KDNSSD/ServiceBrowser>

Public Types

enum  State { Working , Stopped , Unsupported }
 Availability of DNS-SD services. More...
 

Signals

void finished ()
 Emitted when the list of published services has settled.
 
void serviceAdded (KDNSSD::RemoteService::Ptr service)
 Emitted when new service is discovered.
 
void serviceRemoved (KDNSSD::RemoteService::Ptr service)
 Emitted when a service is no longer published over DNS-SD.
 

Public Member Functions

 ServiceBrowser (const QString &type, bool autoResolve=false, const QString &domain=QString(), const QString &subtype=QString())
 Create a ServiceBrowser for a particular service type.
 
bool isAutoResolving () const
 Whether discovered services are resolved before being reported.
 
QList< RemoteService::Ptr > services () const
 The currently known services of the specified type.
 
virtual void startBrowse ()
 Starts browsing for services.
 

Static Public Member Functions

static QString getLocalHostName ()
 The mDNS hostname of the local machine.
 
static State isAvailable ()
 Checks availability of DNS-SD services.
 
static QHostAddress resolveHostName (const QString &hostname)
 Resolves an mDNS hostname into an IP address.
 

Protected Member Functions

virtual void virtual_hook (int, void *)
 

Detailed Description

Browses for network services advertised over DNS-SD.

This is the central class in the KDNSSD library for applications that want to discover services on network.

Suppose that you need list of web servers running. Then you might do something like

KDNSSD::ServiceBrowser *browser = new KDNSSD::ServiceBrowser(QStringLiteral("_http._tcp"));
this, [](KDNSSD::RemoteService::Ptr service) {
});
this, [](KDNSSD::RemoteService::Ptr service) {
});
browser->startBrowse();
Browses for network services advertised over DNS-SD.
Definition servicebrowser.h:55
void serviceRemoved(KDNSSD::RemoteService::Ptr service)
Emitted when a service is no longer published over DNS-SD.
virtual void startBrowse()
Starts browsing for services.
void serviceAdded(KDNSSD::RemoteService::Ptr service)
Emitted when new service is discovered.

In above example addService() will be called for every web server already running and for every web service that subsequently appears on the network and delService() will be called when a server previously advertised is stopped.

Because no domain was passed to constructor, the default domain will be searched. To find other domains to browse for services on, use DomainBrowser.

Author
Jakub Stachowski

Member Enumeration Documentation

◆ State

Availability of DNS-SD services.

Enumerator
Working 

the service is available

Stopped 

not available because mDnsd or Avahi daemon is not running

Unsupported 

not available because KDE was compiled without DNS-SD support

Constructor & Destructor Documentation

◆ ServiceBrowser()

KDNSSD::ServiceBrowser::ServiceBrowser ( const QString &  type,
bool  autoResolve = false,
const QString &  domain = QString(),
const QString &  subtype = QString() 
)
explicit

Create a ServiceBrowser for a particular service type.

DomainBrowser can be used to find other domains to browse on. If no domain is given, the default domain is used.

The service type is the high-level protocol type, followed by a dot, followed by the transport protocol type (_tcp or _udp). The DNS-SD website maintains a full list of service types.

The subtype parameter allows you to do more fine-grained filtering on the services you are interested in. So you might request only FTP servers that allow anonymous access by passing "_ftp._tcp" as the type and "_anon" as the subtype. Subtypes are particularly important for types like _soap and _upnp, which are far too generic for most applications. In these cases, the subtype can be used to specify the particular SOAP or UPnP protocol they want.

Warning
Enabling autoResolve will increase network usage by resolving all services, so this feature should be used only when necessary.
Parameters
typeservice types to browse for (example: "_http._tcp")
autoResolvediscovered services will be resolved before being reported with the serviceAdded() signal
domaina domain to search on instead of the default one
subtypeonly browse for a specific subtype
See also
startBrowse() and isAvailable()

Member Function Documentation

◆ finished

void KDNSSD::ServiceBrowser::finished ( )
signal

Emitted when the list of published services has settled.

This signal is emitted once after startBrowse() is called when all the services of the requested type that are currently published have been reported (even if none are available or the DNS-SD service is not available). It is emitted again when a new batch of services become available or disappear.

For example, if a new host is connected to network and announces some services watched for by this ServiceBrowser, they will be reported by one or more serviceAdded() signals and the whole batch will be concluded by finished().

This signal can be used by applications that just want to get a list of the currently available services (similar to a directory listing) and do not care about adding or removing services that appear or disappear later.

Warning
There is no guarantee any RemoteService pointers received by serviceAdded() will be valid by the time this signal is emitted, so you should either do all your work involving them in the slot receiving the serviceAdded() signal, or you should listen to serviceRemoved() as well.
See also
serviceAdded() and serviceRemoved()

◆ getLocalHostName()

static QString KDNSSD::ServiceBrowser::getLocalHostName ( )
static

The mDNS hostname of the local machine.

Usually this will return the same as QHostInfo::localHostName(), but it may be changed to something different in the Avahi configuration file (if using the Avahi backend).

Returns
the hostname, or an empty string on failure
Since
4.2

◆ isAutoResolving()

bool KDNSSD::ServiceBrowser::isAutoResolving ( ) const

Whether discovered services are resolved before being reported.

Returns
the value of the autoResolve parameter passed to the constructor
Since
4.1

◆ isAvailable()

static State KDNSSD::ServiceBrowser::isAvailable ( )
static

Checks availability of DNS-SD services.

Although this method is part of ServiceBrowser, none of the classes in this library will be able to perform their intended function if this method does not return Working.

If this method does not return Working, it is still safe to call any of the methods in this library. However, no services will be found or published and no domains will be found.

If you use this function to report an error to the user, below is a suggestion on how to word the errors when publishing a service. The first line of each error message can also be used for reporting errors when browsing for services.

return "";
return i18n("<p>The Zeroconf daemon is not running. See the Service"
" Discovery Handbook for more information.<br/>"
"Other users will not see the services provided by this
" system when browsing the network via zeroconf, but "
" normal access will still work.</p>");
case KDNSSD::ServiceBrowser::Unsupported:
return i18n("<p>Zeroconf support is not available in this version of KDE."
" See the Service Discovery Handbook for more information.<br/>"
"Other users will not see the services provided by this
" application when browsing the network via zeroconf, but "
" normal access will still work.</p>");
default:
return i18n("<p>Unknown error with Zeroconf.<br/>"
"Other users will not see the services provided by this
" application when browsing the network via zeroconf, but "
" normal access will still work.</p>");
}
static State isAvailable()
Checks availability of DNS-SD services.
QList< RemoteService::Ptr > services() const
The currently known services of the specified type.
@ Working
the service is available
Definition servicebrowser.h:64
@ Stopped
not available because mDnsd or Avahi daemon is not running
Definition servicebrowser.h:66

◆ resolveHostName()

static QHostAddress KDNSSD::ServiceBrowser::resolveHostName ( const QString &  hostname)
static

Resolves an mDNS hostname into an IP address.

This function is very rarely useful, since a properly configured system is able to resolve an mDNS-based host name using the system resolver (ie: you can just pass the mDNS hostname to KIO or other library).

Parameters
hostnamethe hostname to be resolved
Returns
a QHostAddress containing the IP address, or QHostAddress() if resolution failed
Since
4.2

◆ serviceAdded

void KDNSSD::ServiceBrowser::serviceAdded ( KDNSSD::RemoteService::Ptr  service)
signal

Emitted when new service is discovered.

If isAutoResolving() returns true, this will not be emitted until the service has been resolved.

Parameters
servicea RemoteService object describing the service
See also
serviceRemoved() and finished()

◆ serviceRemoved

void KDNSSD::ServiceBrowser::serviceRemoved ( KDNSSD::RemoteService::Ptr  service)
signal

Emitted when a service is no longer published over DNS-SD.

The RemoteService object is removed from the services() list and deleted immediately after this signal returns.

Warning
Do not use a delayed connection with this signal
Parameters
servicea RemoteService object describing the service
See also
serviceAdded() and finished()

◆ services()

QList< RemoteService::Ptr > KDNSSD::ServiceBrowser::services ( ) const

The currently known services of the specified type.

Returns
a list of RemoteService pointers
See also
serviceAdded() and serviceRemoved()

◆ startBrowse()

virtual void KDNSSD::ServiceBrowser::startBrowse ( )
virtual

Starts browsing for services.

Only the first call to this function will have any effect.

Browsing stops when the ServiceBrowser object is destroyed.

Warning
The serviceAdded() signal may be emitted before this function returns.
See also
serviceAdded(), serviceRemoved() and finished()