/**
* Build packet data
*
* @param int & $length
* @return string
* @throws Exception
*/
public final function build(&$length = 0)
{
if ($this->protocol_type == self::FIXED_ONLY) {
$payload = $this->payload();
} else {
if ($this->protocol_type == self::WITH_VARIABLE) {
$payload = $this->payload();
} else {
if ($this->protocol_type == self::WITH_PAYLOAD) {
$payload = $this->payload();
} else {
throw new Exception('Invalid protocol type');
}
}
}
$length = strlen($payload);
$this->header->setPayloadLength($length);
$length = $this->header->getFullLength();
Debug::Log(Debug::DEBUG, 'Message Build: total length=' . $length);
return $this->header->build() . $payload;
}
/**
* Build fixed Header packet
*
* @return string
* @throws Exception
*/
public function build()
{
$flags = 0;
if (!$this->getQos()) {
if ($this->getDup()) {
/*
In the QoS 0 delivery protocol, the Sender MUST send a PUBLISH packet with QoS=0, DUP=0 [MQTT-4.3.1-1].
*/
throw new Exception('DUP MUST BE 0 if QoS is 0');
}
}
/**
* Flags for fixed Header
*
* This 4-bit number was defined as DUP,QoS 1,QoS 0,RETAIN in MQTT 3.1,
* In 3.1.1, only PUBLISH has those names, for PUBREL, SUBSCRIBE, UNSUBSCRIBE: 0010; and others, 0000
*
* The definition DUP, QoS, RETAIN works in 3.1.1, and literally,
* it means the same for PUBREL, SUBSCRIBE and UNSCRIBE.
*/
$flags |= $this->dup << 3;
$flags |= $this->qos << 1;
$flags |= $this->retain;
$this->reserved_flags = $flags;
return parent::build();
}