SSDP + mDNS Discovery

Phase: J (DLNA / Cast / Discovery) Since: 0.12.0

Overview

Phlix uses two network discovery protocols to detect devices on the local network:

• SSDP (Simple Service Discovery Protocol) — UDP multicast to 239.255.255.250:1900
• mDNS (multicast DNS / Bonjour/Avahi) — UDP multicast to 224.0.0.251:5353

SSDP (UPnP/DLNA Discovery)

Protocol Details

SSDP is part of the UPnP protocol suite and uses HTTP-like messages over UDP.

Multicast Address: 239.255.255.250Port: 1900

Message Types

M-SEARCH (Discovery Request)

M-SEARCH * HTTP/1.1
HOST: 239.255.255.250:1900
MAN: "ssdp:discover"
MX: 3
ST: urn:schemas-upnp-org:device:MediaServer:1
USER-AGENT: Phlix/1.0

NOTIFY (Announcement)

NOTIFY * HTTP/1.1
HOST: 239.255.255.250:1900
NT: urn:schemas-upnp-org:device:MediaServer:1
USN: uuid:phlix-server-{id}::urn:schemas-upnp-org:device:MediaServer:1
LOCATION: http://{ip}:{port}
SERVER: Phlix/1.0 UPnP/1.0
CACHE-CONTROL: max-age=1800

Search Targets (ST)

Device Type	Search Target
All UPnP devices	urn:schemas-upnp-org:device:*
MediaServer	urn:schemas-upnp-org:device:MediaServer:1
MediaRenderer	urn:schemas-upnp-org:device:MediaRenderer:1
ContentDirectory	urn:schemas-upnp-org:service:ContentDirectory:1
ConnectionManager	urn:schemas-upnp-org:service:ConnectionManager:1
AVTransport	urn:schemas-upnp-org:service:AVTransport:1

mDNS (Bonjour/Avahi Discovery)

Protocol Details

mDNS uses DNS-like packets on the local network without a central DNS server.

Multicast Address: 224.0.0.251Port: 5353

Service Types

Service	Type String
Google Cast/Chromecast	_googlecast._tcp.local.
AirPlay 2	_airplay._tcp.local.
AirPlay Audio	_raop._tcp.local.
Roku ECP	_ roku-ecnp._tcp.local.

DNS Record Types

Type	Number	Purpose
PTR	12	Service discovery (pointer to instance)
SRV	33	Service location (host + port)
TXT	16	Service metadata (key-value pairs)
A	1	IPv4 address
AAAA	28	IPv6 address

Architecture

Classes

src/Discovery/
├── Ssdp/
│   ├── SsdpSocket.php       # Raw UDP socket for SSDP
│   ├── SsdpDevice.php      # Discovered device descriptor
│   └── SsdpDiscovery.php    # SSDP discovery service
├── Mdns/
│   ├── MdnsSocket.php       # Raw UDP socket for mDNS
│   ├── MdnsService.php      # Resolved service descriptor
│   └── MdnsDiscovery.php    # mDNS discovery service
├── DiscoveryManager.php      # Unified facade
└── DiscoveryServer.php       # Workerman Timer integration

DiscoveryManager

The DiscoveryManager provides a unified interface for all discovery operations:

$manager->discoverDlnaServers();      // SSDP MediaServers
$manager->discoverDlnaRenderers();    // SSDP MediaRenderers
$manager->discoverChromecastDevices(); // mDNS Chromecast
$manager->discoverAirPlayDevices();    // mDNS AirPlay
$manager->discoverRokuDevices();       // mDNS Roku
$manager->announcePhlixServer();       // Both SSDP + mDNS

Configuration

config/discovery.php:

return [
    'ssdp' => [
        'enabled' => true,
        'announce_interval_secs' => 600,  // SSDP NOTIFY interval
        'discovery_timeout_secs' => 5,
    ],
    'mdns' => [
        'enabled' => true,
        'discovery_timeout_secs' => 5,
    ],
    'discovery_port' => 8200,  // Phlix server port
];

Integration

Workerman Timer

DiscoveryServer uses Workerman's Timer to periodically refresh device lists:

• SSDP discovery: every 60 seconds
• mDNS discovery: every 30 seconds

Start/Stop

$discoveryServer = $container->get(\Phlix\Discovery\DiscoveryServer::class);
$discoveryServer->start();

// Later...
$discoveryServer->stop();

Device Registry

Discovered devices are stored in Dlna\DeviceRegistry for use by other Phase J components (AVTransport, etc.).

Socket Options

Both SSDP and mDNS sockets use these multicast options:

Option	SSDP	mDNS
Multicast TTL	1	255
Loopback	Enabled	Enabled
Reuse Address	Yes	Yes
Receive Timeout	Configurable	Configurable

Error Handling

All socket operations are wrapped in try-catch blocks:

• Network errors return empty arrays
• Invalid responses are skipped
• Errors are logged via PSR-3 logger

Testing

Run unit tests:

./vendor/bin/phpunit tests/unit/Discovery/

Coverage targets:

• SsdpSocket ≥ 85%
• MdnsSocket ≥ 85%
• SsdpDiscovery ≥ 80%
• MdnsDiscovery ≥ 80%
• DiscoveryManager ≥ 80%