# kDNSServiceInterfaceIndexAny ``` var kDNSServiceInterfaceIndexAny: Int32 { get } ``` ## Discussion Specific interface indexes are identified via a 32-bit unsigned integer returned by the if_nametoindex() family of calls. If the client passes 0 for interface index, that means “do the right thing”, which (at present) means, “if the name is in an mDNS local multicast domain (e.g. ‘local.’, ‘254.169.in-addr.arpa.’, ‘{8,9,A,B}.E.F.ip6.arpa.’) then multicast on all applicable interfaces, otherwise send via unicast to the appropriate DNS server.” Normally, most clients will use 0 for interface index to automatically get the default sensible behaviour. If the client passes a positive interface index, then that indicates to do the operation only on that one specified interface. If the client passes [`kDNSServiceInterfaceIndexLocalOnly`](/documentation/dnssd/kDNSServiceInterfaceIndexLocalOnly) when registering a service, then that service will be found *only* by other local clients on the same machine that are browsing using [`kDNSServiceInterfaceIndexLocalOnly`](/documentation/dnssd/kDNSServiceInterfaceIndexLocalOnly) or [`kDNSServiceInterfaceIndexAny`](/documentation/dnssd/kDNSServiceInterfaceIndexAny). If a client has a ‘private’ service, accessible only to other processes running on the same machine, this allows the client to advertise that service in a way such that it does not inadvertently appear in service lists on all the other machines on the network. If the client passes [`kDNSServiceInterfaceIndexLocalOnly`](/documentation/dnssd/kDNSServiceInterfaceIndexLocalOnly) when browsing then it will find *all* records registered on that same local machine. Clients explicitly wishing to discover *only* LocalOnly services can accomplish this by inspecting the interfaceIndex of each service reported to their [`DNSServiceBrowseReply`](/documentation/dnssd/DNSServiceBrowseReply) callback function, and discarding those where the interface index is not [`kDNSServiceInterfaceIndexLocalOnly`](/documentation/dnssd/kDNSServiceInterfaceIndexLocalOnly). [`kDNSServiceInterfaceIndexP2P`](/documentation/dnssd/kDNSServiceInterfaceIndexP2P) is meaningful only in Browse, QueryRecord, Register, and Resolve operations. It should not be used in other DNSService APIs. - If [`kDNSServiceInterfaceIndexP2P`](/documentation/dnssd/kDNSServiceInterfaceIndexP2P) is passed to [`DNSServiceBrowse(_:_:_:_:_:_:_:)`](/documentation/dnssd/DNSServiceBrowse(_:_:_:_:_:_:_:)) or [`DNSServiceQueryRecord(_:_:_:_:_:_:_:_:)`](/documentation/dnssd/DNSServiceQueryRecord(_:_:_:_:_:_:_:_:)), it restricts the operation to P2P. - If kDNSServiceInterfaceIndexP2P is passed to DNSServiceRegister, it is mapped internally to kDNSServiceInterfaceIndexAny with the kDNSServiceFlagsIncludeP2P set. - If [`kDNSServiceInterfaceIndexP2P`](/documentation/dnssd/kDNSServiceInterfaceIndexP2P) is passed to [`DNSServiceResolve(_:_:_:_:_:_:_:_:)`](/documentation/dnssd/DNSServiceResolve(_:_:_:_:_:_:_:_:)), it is mapped internally to [`kDNSServiceInterfaceIndexAny`](/documentation/dnssd/kDNSServiceInterfaceIndexAny) with the kDNSServiceFlagsIncludeP2P set, because resolving a P2P service may create and/or enable an interface whose index is not known a priori. The resolve callback will indicate the index of the interface via which the service can be accessed. If applications pass [`kDNSServiceInterfaceIndexAny`](/documentation/dnssd/kDNSServiceInterfaceIndexAny) to [`DNSServiceBrowse(_:_:_:_:_:_:_:)`](/documentation/dnssd/DNSServiceBrowse(_:_:_:_:_:_:_:)) or [`DNSServiceQueryRecord(_:_:_:_:_:_:_:_:)`](/documentation/dnssd/DNSServiceQueryRecord(_:_:_:_:_:_:_:_:)), they must set the kDNSServiceFlagsIncludeP2P flag to include P2P. In this case, if a service instance or the record being queried is found over P2P, the resulting ADD event will indicate [`kDNSServiceInterfaceIndexP2P`](/documentation/dnssd/kDNSServiceInterfaceIndexP2P) as the interface index. --- Copyright © 2026 Apple Inc. All rights reserved. | [Terms of Use](https://www.apple.com/legal/internet-services/terms/site.html) | [Privacy Policy](https://www.apple.com/privacy/privacy-policy)