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($wait = 15)
{
// 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
$firstresponsetime = -1;
$lastpackettime = -1;
$starttime = round(microtime(true) * 1000);
$mdns->query("_googlecast._tcp.local", 1, 12, "");
$mdns->query("_googlecast._tcp.local", 1, 12, "");
$mdns->query("_googlecast._tcp.local", 1, 12, "");
$cc = $wait;
set_time_limit($wait * 2);
$chromecasts = [];
while ($cc > 0) {
$inpacket = "";
while ($inpacket == "") {
$inpacket = $mdns->readIncoming();
if ($inpacket <> "") {
if ($inpacket->packetheader->getQuestions() > 0) {
$inpacket = "";
}
}
if ($lastpackettime <> -1) {
// If we get to here then we have a valid last packet time
$timesincelastpacket = round(microtime(true) * 1000) - $lastpackettime;
if ($timesincelastpacket > ($firstresponsetime * 5) && $firstresponsetime != -1) {
return $chromecasts;
}
}
if ($inpacket <> "") {
$lastpackettime = round(microtime(true) * 1000);
}
$timetohere = round(microtime(true) * 1000) - $starttime;
// Maximum five second rule
if ($timetohere > 5000) {
return $chromecasts;
}
}
// If our packet has answers, then read them
// $mdns->printPacket($inpacket);
if ($inpacket->packetheader->getAnswerRRs() > 0) {
// $mdns->printPacket($inpacket);
for ($x = 0; $x < sizeof($inpacket->answerrrs); $x++) {
if ($inpacket->answerrrs[$x]->qtype == 12) {
// print_r($inpacket->answerrrs[$x]);
if ($inpacket->answerrrs[$x]->name == "_googlecast._tcp.local") {
if ($firstresponsetime == -1) {
$firstresponsetime = round(microtime(true) * 1000) - $starttime;
}
$name = "";
for ($y = 0; $y < sizeof($inpacket->answerrrs[$x]->data); $y++) {
$name .= chr($inpacket->answerrrs[$x]->data[$y]);
}
// The chromecast itself fills in additional rrs. So if that's there then we have a quicker method of
// processing the results.
// First build any missing entries with any 33 packets we find.
for ($p = 0; $p < sizeof($inpacket->additionalrrs); $p++) {
if ($inpacket->additionalrrs[$p]->qtype == 33) {
$d = $inpacket->additionalrrs[$p]->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]);
}
$target .= ".local";
if (!isset($chromecasts[$inpacket->additionalrrs[$p]->name])) {
$chromecasts[$inpacket->additionalrrs[$x]->name] = array(
"port" => $port,
"ip" => "",
"target" => "",
"friendly_name" => ""
);
}
$chromecasts[$inpacket->additionalrrs[$x]->name]['target'] = $target;
}
}
// Next repeat the process for 16
for ($p = 0; $p < sizeof($inpacket->additionalrrs); $p++) {
if ($inpacket->additionalrrs[$p]->qtype == 16) {
$fn = "";
for ($q = 0; $q < sizeof($inpacket->additionalrrs[$p]->data); $q++) {
$fn .= chr($inpacket->additionalrrs[$p]->data[$q]);
}
$stp = strpos($fn, "fn=") + 3;
$etp = strpos($fn, "ca=");
$fn = substr($fn, $stp, $etp - $stp - 1);
if (!isset($chromecasts[$inpacket->additionalrrs[$p]->name])) {
$chromecasts[$inpacket->additionalrrs[$x]->name] = array(
"port" => 8009,
"ip" => "",
"target" => "",
"friendly_name" => ""
);
}
$chromecasts[$inpacket->additionalrrs[$x]->name]['friendly_name'] = $fn;
}
}
// And finally repeat again for 1
for ($p = 0; $p < sizeof($inpacket->additionalrrs); $p++) {
if ($inpacket->additionalrrs[$p]->qtype == 1) {
$d = $inpacket->additionalrrs[$p]->data;
$ip = $d[0] . "." . $d[1] . "." . $d[2] . "." . $d[3];
foreach ($chromecasts as $key => $value) {
if ($value['target'] == $inpacket->additionalrrs[$p]->name) {
$value['ip'] = $ip;
$chromecasts[$key] = $value;
}
}
}
}
$dontrequery = 1;
// Check our item. If it doesn't exist then it wasn't in the additionals, so send requests.
// If it does exist then check it has all the items. If not, send the requests.
if (isset($chromecasts[$name])) {
$xx = $chromecasts[$name];
if ($xx['target'] == "") {
// Send a 33 request
$mdns->query($name, 1, 33, "");
$dontrequery = 0;
}
if ($xx['friendly_name'] == "") {
// Send a 16 request
$mdns->query($name, 1, 16, "");
$dontrequery = 0;
}
if ($xx['target'] != "" && $xx['friendly_name'] != "" && $xx['ip'] == "") {
// Only missing the ip address for the target.
$mdns->query($xx['target'], 1, 1, "");
$dontrequery = 0;
}
} else {
// Send queries. These'll trigger a 1 query when we have a target name.
$mdns->query($name, 1, 33, "");
$mdns->query($name, 1, 16, "");
$dontrequery = 0;
}
if ($dontrequery == 0) {
$cc = $wait;
}
set_time_limit($wait * 2);
}
}
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]);
}
$target .= ".local";
if (!isset($chromecasts[$inpacket->answerrrs[$x]->name])) {
$chromecasts[$inpacket->answerrrs[$x]->name] = array(
"port" => $port,
"ip" => "",
"target" => $target,
"friendly_name" => ""
);
} else {
$chromecasts[$inpacket->answerrrs[$x]->name]['target'] = $target;
}
// We know the name and port. Send an A query for the IP address
$mdns->query($target, 1, 1, "");
$cc = $wait;
set_time_limit($wait * 2);
}
if ($inpacket->answerrrs[$x]->qtype == 16) {
$fn = "";
for ($q = 0; $q < sizeof($inpacket->answerrrs[$x]->data); $q++) {
$fn .= chr($inpacket->answerrrs[$x]->data[$q]);
}
$stp = strpos($fn, "fn=") + 3;
$etp = strpos($fn, "ca=");
$fn = substr($fn, $stp, $etp - $stp - 1);
if (!isset($chromecasts[$inpacket->answerrrs[$x]->name])) {
$chromecasts[$inpacket->answerrrs[$x]->name] = array(
"port" => 8009,
"ip" => "",
"target" => "",
"friendly_name" => $fn
);
} else {
$chromecasts[$inpacket->answerrrs[$x]->name]['friendly_name'] = $fn;
}
$mdns->query($chromecasts[$inpacket->answerrrs[$x]->name]['target'], 1, 1, "");
$cc = $wait;
set_time_limit($wait * 2);
}
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] = $value;
// If we have an IP address but no friendly name, try and get the friendly name again!
if (strlen($value['friendly_name']) < 1) {
$mdns->query($key, 1, 16, "");
$cc = $wait;
set_time_limit($wait * 2);
}
}
}
}
}
}
$cc--;
}
return $chromecasts;
}
``