Service discovery
Overview
AirPlay devices do service discovery through multicast DNS (mDNS) and the zeroconf protocol. Apple is known to use its own implementation called Bonjour. The communication between sender and receiver can take place on port 7000/TCP or on any other TCP port declared by the receiver in its mDNS record.
_airplay._tcp.
The _airplay service appeared when AirPlay was initially introduced. This is also the service AirPlay 2 is currently using.
An AirPlay 2 sender inspects the following TXT records, including all the _raop._tcp entries and adding new ones. features is the most important record and controls what are the “inner” properties of an AirPlay receiver. It's analyzed in the following section, Features.
| FromTXTRecord | ToDict | Type | Explanation |
|---|---|---|---|
| fv | firmwareVersion | String | Firmware version |
| acl | accessControlLevel | Int64 | Access control level |
| btaddr | bluetoothAddress | String | Bluetooth address |
| deviceid | deviceID | String | Device ID |
| features | features | Int64 | Features |
| rsf | requiredSenderFeatures | Int64 | Required sender features |
| flags | systemFlags | Int64 | System flags |
| gcgl | groupContainsDiscoverableLeader | Boolean | Group contains discoverable leader |
| gid | groupUUID | String | Group UUID |
| gpn | groupPublicName | String | Group public name |
| igl | isGroupLeader | Boolean | Is group leader |
| hgid | homeGroupUUID | String | Home group UUID |
| hmid | householdID | String | Household ID |
| pgcgl | parentGroupContainsDiscoverableLeader | Boolean | Parent group contains discoverable leader |
| pgid | parentGroupUUID | String | Parent group UUID |
| tsid | tightSyncUUID | String | Tight sync UUID |
| hkid | homeKitHomeUUID | String | HomeKit home UUID |
| model | deviceModel | String | Device model |
| manufacturer | manufacturer | String | Manufacturer |
| serialNumber | serialNumber | String | Serial number |
| protovers | protocolVersion | String | Protocol version |
| pi | publicCUAirPlayPairingIdentity | String | Public CU AirPlay pairing identity |
| psi | publicCUSystemPairingIdentity | String | Public CU System Pairing Identity |
| pk | publicKey | String | Public key |
| srcvers | airPlayVersion | String | AirPlay version |
| osvers | OSVersion | String | OS version |
Example: mDNS for a Sonos One receiver
acl=0 deviceid=AA:BB:CC:DD:EE:FF features=0x445F8A00,0x1C340 rsf=0x0 fv=p20.53.3-71050 flags=0x404 model=One manufacturer=Sonos serialNumber=AA-BB-CC-DD-EE-FF:6 protovers=1.1 srcvers=366.0 pi=<UUID> gid=<UUID> gcgl=0 pk=<32B hex encoded public key>
_airplay-p2p._tcp.
The _airplay-p2p service was introduced to stream content to Apple TVs without having to be connected to the same local network.
_raop._tcp.
RAOP stands for Remote Audio Output Protocol. The _raop service was introduced for audio streaming only when _airplay was supporting only photo and video streaming only
| FromTXTRecord | ToDict | Type | Explanation |
|---|---|---|---|
| cn | compressionTypes | BitList | Compression types |
| da | rfc2617DigestAuthKey | Boolean | RFC2617 digest auth key |
| et | encryptionTypes | BitList | Encryption types |
| ft | features | Int64 | Features |
| fv | firmwareVersion | String | Firmware version |
| sf | systemFlags | Int64 | System flags |
| md | metadataTypes | BitList | Metadata types |
| am | deviceModel | String | Device model |
| pw | password | Boolean | Password |
| pk | publicKey | String | Public key |
| tp | transportTypes | String | Transport types |
| vn | airTunesProtocolVersion | String | AirTunes protocol version |
| vs | airPlayVersion | String | AirPlay version |
| ov | OSVersion | String | OS version |
| vv | vodkaVersion | Int64 | Vodka version |
