Class MqttCodec

java.lang.Object

com.codename1.io.mqtt.MqttCodec

public final class MqttCodec
extends Object

Encodes and decodes MQTT 3.1.1 control packets on plain streams, so it is independent of the transport. QoS 2 packets (PUBREC, PUBREL, PUBCOMP) and a PUBLISH at QoS 2 are rejected with an MqttException.

Field Summary

Fields

Modifier and Type	Field	Description
static final int	MAX_REMAINING_LENGTH	The largest remaining length the protocol can express, 268435455.

Method Summary

Modifier and Type	Method	Description
static MqttPacket	decode(int first, byte[] body)	Decodes a packet from its first byte and its body.
static byte[]	encode(MqttPacket p)	Encodes a packet to its wire form.
static byte[]	encodeRemainingLength(int value)	Encodes a remaining length as the protocol's variable length integer.
static int	packetLength(byte[] buf, int off, int len, int maxRemaining)	Measures the first packet in a buffer.
static MqttPacket	read(InputStream in, int maxRemaining)	Reads one packet from a stream, blocking until it is complete.
static void	write(MqttPacket p, OutputStream out)	Encodes a packet and writes it to a stream, without flushing it.

Methods inherited from class Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Details

MAX_REMAINING_LENGTH

public static final int MAX_REMAINING_LENGTH

The largest remaining length the protocol can express, 268435455.

See Also:

• Constant Field Values

Method Details

encodeRemainingLength

public static byte[] encodeRemainingLength(int value)

Encodes a remaining length as the protocol's variable length integer.

Parameters

• value: 0 to 268435455

Returns

one to four bytes

encode

public static byte[] encode(MqttPacket p)
                     throws IOException

Encodes a packet to its wire form.

Parameters

• p: the packet

Returns

the fixed header followed by the variable header and payload

Throws

MqttException when the packet cannot be represented

Throws:

IOException

write

public static void write(MqttPacket p,
 OutputStream out)
                  throws IOException

Encodes a packet and writes it to a stream, without flushing it.

Parameters

• p: the packet

• out: the destination

Throws:

IOException

packetLength

public static int packetLength(byte[] buf,
 int off,
 int len,
 int maxRemaining)
                        throws IOException

Measures the first packet in a buffer.

Parameters

• buf: received bytes

• off: where the packet starts

• len: how many bytes are available from off

• maxRemaining: the largest remaining length to accept

Returns

the total size of the packet, fixed header included, or -1 when more bytes are needed

Throws

MqttException when the length is malformed or above the limit

Throws:

IOException

read

public static MqttPacket read(InputStream in,
 int maxRemaining)
                       throws IOException

Reads one packet from a stream, blocking until it is complete.

Parameters

• in: the source

• maxRemaining: the largest remaining length to accept

Returns

the packet

Throws

EOFException when the stream ends, MqttException for a malformed or oversized packet

Throws:

IOException

decode

public static MqttPacket decode(int first,
 byte[] body)
                         throws IOException

Decodes a packet from its first byte and its body.

Parameters

• first: the fixed header's first byte (type and flags)

• body: the bytes after the remaining length

Returns

the packet

Throws:

IOException