PHPmDNS

class for mDNS querying from PHP

Note: this class is not full featured but is the beginnings of an mDNS library. At the moment it can perform A, SRV, PTR queries.

Example of scanning for chromecasts

	public static function scan() {
		// Performs an mdns scan of the network to find chromecasts and returns an array
		// Let's test by finding Google Chromecasts
		$mdns = new mDNS();
		// Search for chromecast devices
		// For a bit more surety, send multiple search requests
		$mdns->query("_googlecast._tcp.local",1,12,"");
		$mdns->query("_googlecast._tcp.local",1,12,"");
		$mdns->query("_googlecast._tcp.local",1,12,"");
		$cc = 15;
		$chromecasts = array();
		while ($cc>0) {
			$inpacket = $mdns->readIncoming();
			//$mdns->printPacket($inpacket);
			// If our packet has answers, then read them
			if ($inpacket->packetheader->getAnswerRRs()> 0) {
				for ($x=0; $x < sizeof($inpacket->answerrrs); $x++) {
					if ($inpacket->answerrrs[$x]->qtype == 12) {
						//print_r($inpacket->answerrrs[$x]);
						if ($inpacket->answerrrs[$x]->name == "_googlecast._tcp.local") {
							$name = "";
							for ($y = 0; $y < sizeof($inpacket->answerrrs[$x]->data); $y++) {
								$name .= chr($inpacket->answerrrs[$x]->data[$y]);
							}
							// The chromecast name is in $name. Send a a SRV query
							$mdns->query($name, 1, 33, "");
							$cc=15;
						}
					}
					if ($inpacket->answerrrs[$x]->qtype == 33) {
						$d = $inpacket->answerrrs[$x]->data;
						$port = ($d[4] * 256) + $d[5];
						// We need the target from the data
						$offset = 6;
						$size = $d[$offset];
						$offset++;
						$target = "";
						for ($z=0; $z < $size; $z++) {
							$target .= chr($d[$offset + $z]);
						}
						$target .= ".local";
						$chromecasts[$inpacket->answerrrs[$x]->name] = array("port"=>$port, "ip"=>"", "target"=>$target);
						// We know the name and port. Send an A query for the IP address
						$mdns->query($target,1,1,"");
						$cc=15;
					}
					if ($inpacket->answerrrs[$x]->qtype == 1) {
						$d = $inpacket->answerrrs[$x]->data;
						$ip = $d[0] . "." . $d[1] . "." . $d[2] . "." . $d[3];
						// Loop through the chromecasts and fill in the ip
						foreach ($chromecasts as $key=>$value) {
							if ($value['target'] == $inpacket->answerrrs[$x]->name) {
								$value['ip'] = $ip;	
								$chromecasts[$key] = $value;
							}
						}
					}
				}
			}
			$cc--;
		}

		return $chromecasts;
	}
``