--- title: dnssd framework: dnssd role: collection role_heading: Framework path: dnssd --- # dnssd Discover, publish, and resolve network services on a local area or wide area network. ## Overview Overview The DNS Service Discovery API helps you to perform three main tasks: Registering a service. Browsing for services. Resolving service names to host names. In support of these main tasks, this API can directly assist you in performing two subsidiary tasks: Enumerating domains (finding recommended service domains). Updating registrations (changing your DNS registration data dynamically). Most apps shouldn’t use this API, and instead should use a higher-level service discovery API like NetService. Use dnssd if you’re writing BSD-style applications or cross-platform programs that don’t need to link to higher-level frameworks. You can also use dnssd if you need specific lower-level functionality exposed by this API. important: Apps that use the local network must provide a usage string in their Info.plist file with the key NSLocalNetworkUsageDescription. Apps that use Bonjour must also declare the services they browse, using the NSBonjourServices key. ## Topics ### Reference - [DNS Service Discovery C](dnssd/dns-service-discovery-c.md) - [dnssd Enumerations](dnssd/dnssd-enumerations.md) - [dnssd Functions](dnssd/dnssd-functions.md) - [dnssd Data Types](dnssd/dnssd-data-types.md) - [dnssd Constants](dnssd/dnssd-constants.md) ### Variables - [kDNSServiceAAAAPolicyFallback](dnssd/kdnsserviceaaaapolicyfallback.md) - [kDNSServiceAAAAPolicyNone](dnssd/kdnsserviceaaaapolicynone.md) - [kDNSServiceClass_IN](dnssd/kdnsserviceclass_in.md) - [kDNSServiceErr_AWDLTimeout](dnssd/kdnsserviceerr_awdltimeout.md) - [kDNSServiceErr_AlreadyRegistered](dnssd/kdnsserviceerr_alreadyregistered.md) - [kDNSServiceErr_BadFlags](dnssd/kdnsserviceerr_badflags.md) - [kDNSServiceErr_BadInterfaceIndex](dnssd/kdnsserviceerr_badinterfaceindex.md) - [kDNSServiceErr_BadKey](dnssd/kdnsserviceerr_badkey.md) - [kDNSServiceErr_BadParam](dnssd/kdnsserviceerr_badparam.md) - [kDNSServiceErr_BadReference](dnssd/kdnsserviceerr_badreference.md) - [kDNSServiceErr_BadSig](dnssd/kdnsserviceerr_badsig.md) - [kDNSServiceErr_BadState](dnssd/kdnsserviceerr_badstate.md) - [kDNSServiceErr_BadTime](dnssd/kdnsserviceerr_badtime.md) - [kDNSServiceErr_DefunctConnection](dnssd/kdnsserviceerr_defunctconnection.md) - [kDNSServiceErr_DoubleNAT](dnssd/kdnsserviceerr_doublenat.md) - [kDNSServiceErr_Firewall](dnssd/kdnsserviceerr_firewall.md) - [kDNSServiceErr_Incompatible](dnssd/kdnsserviceerr_incompatible.md) - [kDNSServiceErr_Invalid](dnssd/kdnsserviceerr_invalid.md) - [kDNSServiceErr_NATPortMappingDisabled](dnssd/kdnsserviceerr_natportmappingdisabled.md) - [kDNSServiceErr_NATPortMappingUnsupported](dnssd/kdnsserviceerr_natportmappingunsupported.md) - [kDNSServiceErr_NATTraversal](dnssd/kdnsserviceerr_nattraversal.md) - [kDNSServiceErr_NameConflict](dnssd/kdnsserviceerr_nameconflict.md) - [kDNSServiceErr_NoAuth](dnssd/kdnsserviceerr_noauth.md) - [kDNSServiceErr_NoError](dnssd/kdnsserviceerr_noerror.md) - [kDNSServiceErr_NoMemory](dnssd/kdnsserviceerr_nomemory.md) - [kDNSServiceErr_NoRouter](dnssd/kdnsserviceerr_norouter.md) - [kDNSServiceErr_NoSuchKey](dnssd/kdnsserviceerr_nosuchkey.md) - [kDNSServiceErr_NoSuchName](dnssd/kdnsserviceerr_nosuchname.md) - [kDNSServiceErr_NoSuchRecord](dnssd/kdnsserviceerr_nosuchrecord.md) - [kDNSServiceErr_NotInitialized](dnssd/kdnsserviceerr_notinitialized.md) - [kDNSServiceErr_NotPermitted](dnssd/kdnsserviceerr_notpermitted.md) - [kDNSServiceErr_PolicyDenied](dnssd/kdnsserviceerr_policydenied.md) - [kDNSServiceErr_PollingMode](dnssd/kdnsserviceerr_pollingmode.md) - [kDNSServiceErr_Refused](dnssd/kdnsserviceerr_refused.md) - [kDNSServiceErr_ServiceNotRunning](dnssd/kdnsserviceerr_servicenotrunning.md) - [kDNSServiceErr_StaleData](dnssd/kdnsserviceerr_staledata.md) - [kDNSServiceErr_Timeout](dnssd/kdnsserviceerr_timeout.md) - [kDNSServiceErr_Transient](dnssd/kdnsserviceerr_transient.md) - [kDNSServiceErr_Unknown](dnssd/kdnsserviceerr_unknown.md) - [kDNSServiceErr_Unsupported](dnssd/kdnsserviceerr_unsupported.md) - [kDNSServiceFlagAnsweredFromCache](dnssd/kdnsserviceflagansweredfromcache.md) - [kDNSServiceFlagsAdd](dnssd/kdnsserviceflagsadd.md) - [kDNSServiceFlagsAllowExpiredAnswers](dnssd/kdnsserviceflagsallowexpiredanswers.md) - [kDNSServiceFlagsAllowRemoteQuery](dnssd/kdnsserviceflagsallowremotequery.md) - [kDNSServiceFlagsAutoTrigger](dnssd/kdnsserviceflagsautotrigger.md) - [kDNSServiceFlagsBackgroundTrafficClass](dnssd/kdnsserviceflagsbackgroundtrafficclass.md) - [kDNSServiceFlagsBogus](dnssd/kdnsserviceflagsbogus.md) - [kDNSServiceFlagsBrowseDomains](dnssd/kdnsserviceflagsbrowsedomains.md) - [kDNSServiceFlagsDefault](dnssd/kdnsserviceflagsdefault.md) - [kDNSServiceFlagsEnableDNSSEC](dnssd/kdnsserviceflagsenablednssec.md) - [kDNSServiceFlagsExpiredAnswer](dnssd/kdnsserviceflagsexpiredanswer.md) - [kDNSServiceFlagsForce](dnssd/kdnsserviceflagsforce.md) - [kDNSServiceFlagsForceMulticast](dnssd/kdnsserviceflagsforcemulticast.md) - [kDNSServiceFlagsIncludeAWDL](dnssd/kdnsserviceflagsincludeawdl.md) - [kDNSServiceFlagsIncludeP2P](dnssd/kdnsserviceflagsincludep2p.md) - [kDNSServiceFlagsIndeterminate](dnssd/kdnsserviceflagsindeterminate.md) - [kDNSServiceFlagsInsecure](dnssd/kdnsserviceflagsinsecure.md) - [kDNSServiceFlagsKnownUnique](dnssd/kdnsserviceflagsknownunique.md) - [kDNSServiceFlagsLongLivedQuery](dnssd/kdnsserviceflagslonglivedquery.md) - [kDNSServiceFlagsMoreComing](dnssd/kdnsserviceflagsmorecoming.md) - [kDNSServiceFlagsNoAutoRename](dnssd/kdnsserviceflagsnoautorename.md) - [kDNSServiceFlagsPrivateFive](dnssd/kdnsserviceflagsprivatefive.md) - [kDNSServiceFlagsPrivateFour](dnssd/kdnsserviceflagsprivatefour.md) - [kDNSServiceFlagsPrivateOne](dnssd/kdnsserviceflagsprivateone.md) - [kDNSServiceFlagsPrivateThree](dnssd/kdnsserviceflagsprivatethree.md) - [kDNSServiceFlagsPrivateTwo](dnssd/kdnsserviceflagsprivatetwo.md) - [kDNSServiceFlagsQueueRequest](dnssd/kdnsserviceflagsqueuerequest.md) - [kDNSServiceFlagsRegistrationDomains](dnssd/kdnsserviceflagsregistrationdomains.md) - [kDNSServiceFlagsReturnIntermediates](dnssd/kdnsserviceflagsreturnintermediates.md) - [kDNSServiceFlagsSecure](dnssd/kdnsserviceflagssecure.md) - [kDNSServiceFlagsShareConnection](dnssd/kdnsserviceflagsshareconnection.md) - [kDNSServiceFlagsShared](dnssd/kdnsserviceflagsshared.md) - [kDNSServiceFlagsSuppressUnusable](dnssd/kdnsserviceflagssuppressunusable.md) - [kDNSServiceFlagsThresholdFinder](dnssd/kdnsserviceflagsthresholdfinder.md) - [kDNSServiceFlagsThresholdOne](dnssd/kdnsserviceflagsthresholdone.md) - [kDNSServiceFlagsThresholdReached](dnssd/kdnsserviceflagsthresholdreached.md) - [kDNSServiceFlagsTimeout](dnssd/kdnsserviceflagstimeout.md) - [kDNSServiceFlagsUnicastResponse](dnssd/kdnsserviceflagsunicastresponse.md) - [kDNSServiceFlagsUnique](dnssd/kdnsserviceflagsunique.md) - [kDNSServiceFlagsValidate](dnssd/kdnsserviceflagsvalidate.md) - [kDNSServiceFlagsValidateOptional](dnssd/kdnsserviceflagsvalidateoptional.md) - [kDNSServiceFlagsWakeOnResolve](dnssd/kdnsserviceflagswakeonresolve.md) - [kDNSServiceFlagsWakeOnlyService](dnssd/kdnsserviceflagswakeonlyservice.md) - [kDNSServiceProtocol_IPv4](dnssd/kdnsserviceprotocol_ipv4.md) - [kDNSServiceProtocol_IPv6](dnssd/kdnsserviceprotocol_ipv6.md) - [kDNSServiceProtocol_TCP](dnssd/kdnsserviceprotocol_tcp.md) - [kDNSServiceProtocol_UDP](dnssd/kdnsserviceprotocol_udp.md) - [kDNSServiceType_A](dnssd/kdnsservicetype_a.md) - [kDNSServiceType_A6](dnssd/kdnsservicetype_a6.md) - [kDNSServiceType_AAAA](dnssd/kdnsservicetype_aaaa.md) - [kDNSServiceType_AFSDB](dnssd/kdnsservicetype_afsdb.md) - [kDNSServiceType_ANY](dnssd/kdnsservicetype_any.md) - [kDNSServiceType_APL](dnssd/kdnsservicetype_apl.md) - [kDNSServiceType_ATMA](dnssd/kdnsservicetype_atma.md) - [kDNSServiceType_AXFR](dnssd/kdnsservicetype_axfr.md) - [kDNSServiceType_CERT](dnssd/kdnsservicetype_cert.md) - [kDNSServiceType_CNAME](dnssd/kdnsservicetype_cname.md) - [kDNSServiceType_DHCID](dnssd/kdnsservicetype_dhcid.md) - [kDNSServiceType_DNAME](dnssd/kdnsservicetype_dname.md) - [kDNSServiceType_DNSKEY](dnssd/kdnsservicetype_dnskey.md) - [kDNSServiceType_DS](dnssd/kdnsservicetype_ds.md) - [kDNSServiceType_EID](dnssd/kdnsservicetype_eid.md) - [kDNSServiceType_GID](dnssd/kdnsservicetype_gid.md) - [kDNSServiceType_GPOS](dnssd/kdnsservicetype_gpos.md) - [kDNSServiceType_HINFO](dnssd/kdnsservicetype_hinfo.md) - [kDNSServiceType_HIP](dnssd/kdnsservicetype_hip.md) - [kDNSServiceType_HTTPS](dnssd/kdnsservicetype_https.md) - [kDNSServiceType_IPSECKEY](dnssd/kdnsservicetype_ipseckey.md) - [kDNSServiceType_ISDN](dnssd/kdnsservicetype_isdn.md) - [kDNSServiceType_IXFR](dnssd/kdnsservicetype_ixfr.md) - [kDNSServiceType_KEY](dnssd/kdnsservicetype_key.md) - [kDNSServiceType_KX](dnssd/kdnsservicetype_kx.md) - [kDNSServiceType_LOC](dnssd/kdnsservicetype_loc.md) - [kDNSServiceType_MAILA](dnssd/kdnsservicetype_maila.md) - [kDNSServiceType_MAILB](dnssd/kdnsservicetype_mailb.md) - [kDNSServiceType_MB](dnssd/kdnsservicetype_mb.md) - [kDNSServiceType_MD](dnssd/kdnsservicetype_md.md) - [kDNSServiceType_MF](dnssd/kdnsservicetype_mf.md) - [kDNSServiceType_MG](dnssd/kdnsservicetype_mg.md) - [kDNSServiceType_MINFO](dnssd/kdnsservicetype_minfo.md) - [kDNSServiceType_MR](dnssd/kdnsservicetype_mr.md) - [kDNSServiceType_MX](dnssd/kdnsservicetype_mx.md) - [kDNSServiceType_NAPTR](dnssd/kdnsservicetype_naptr.md) - [kDNSServiceType_NIMLOC](dnssd/kdnsservicetype_nimloc.md) - [kDNSServiceType_NS](dnssd/kdnsservicetype_ns.md) - [kDNSServiceType_NSAP](dnssd/kdnsservicetype_nsap.md) - [kDNSServiceType_NSAP_PTR](dnssd/kdnsservicetype_nsap_ptr.md) - [kDNSServiceType_NSEC](dnssd/kdnsservicetype_nsec.md) - [kDNSServiceType_NSEC3](dnssd/kdnsservicetype_nsec3.md) - [kDNSServiceType_NSEC3PARAM](dnssd/kdnsservicetype_nsec3param.md) - [kDNSServiceType_NULL](dnssd/kdnsservicetype_null.md) - [kDNSServiceType_NXT](dnssd/kdnsservicetype_nxt.md) - [kDNSServiceType_OPT](dnssd/kdnsservicetype_opt.md) - [kDNSServiceType_PTR](dnssd/kdnsservicetype_ptr.md) - [kDNSServiceType_PX](dnssd/kdnsservicetype_px.md) - [kDNSServiceType_RP](dnssd/kdnsservicetype_rp.md) - [kDNSServiceType_RRSIG](dnssd/kdnsservicetype_rrsig.md) - [kDNSServiceType_RT](dnssd/kdnsservicetype_rt.md) - [kDNSServiceType_SIG](dnssd/kdnsservicetype_sig.md) - [kDNSServiceType_SINK](dnssd/kdnsservicetype_sink.md) - [kDNSServiceType_SOA](dnssd/kdnsservicetype_soa.md) - [kDNSServiceType_SPF](dnssd/kdnsservicetype_spf.md) - [kDNSServiceType_SRV](dnssd/kdnsservicetype_srv.md) - [kDNSServiceType_SSHFP](dnssd/kdnsservicetype_sshfp.md) - [kDNSServiceType_SVCB](dnssd/kdnsservicetype_svcb.md) - [kDNSServiceType_TKEY](dnssd/kdnsservicetype_tkey.md) - [kDNSServiceType_TSIG](dnssd/kdnsservicetype_tsig.md) - [kDNSServiceType_TXT](dnssd/kdnsservicetype_txt.md) - [kDNSServiceType_UID](dnssd/kdnsservicetype_uid.md) - [kDNSServiceType_UINFO](dnssd/kdnsservicetype_uinfo.md) - [kDNSServiceType_UNSPEC](dnssd/kdnsservicetype_unspec.md) - [kDNSServiceType_WKS](dnssd/kdnsservicetype_wks.md) - [kDNSServiceType_X25](dnssd/kdnsservicetype_x25.md)