MQTTPacket.c File Reference

functions to deal with reading and writing of MQTT packets from and to sockets More...

#include "MQTTPacket.h"
#include "Log.h"
#include "MQTTPersistence.h"
#include "Messages.h"
#include "StackTrace.h"
#include "WebSocket.h"
#include "MQTTTime.h"
#include <stdlib.h>
#include <string.h>
#include "Heap.h"

Include dependency graph for MQTTPacket.c:

Macros
#define	min(A, B)   ( (A) < (B) ? (A):(B))
#define	MAX_NO_OF_REMAINING_LENGTH_BYTES   4
#define	MAX_NO_OF_REMAINING_LENGTH_BYTES   4

Functions
const char *	MQTTPacket_name (int ptype)
	Converts an MQTT packet code into its name. More...
static char *	readUTFlen (char **pptr, char *enddata, int *len)
	Reads a "UTF" string from the input buffer. More...
static int	MQTTPacket_send_ack (int MQTTVersion, int type, int msgid, int dup, networkHandles *net)
	Send an MQTT acknowledgement packet down a socket. More...
void *	MQTTPacket_Factory (int MQTTVersion, networkHandles *net, int *error)
	Reads one MQTT packet from a socket. More...
int	MQTTPacket_send (networkHandles *net, Header header, char *buffer, size_t buflen, int freeData, int MQTTVersion)
	Sends an MQTT packet in one system call write. More...
int	MQTTPacket_sends (networkHandles *net, Header header, PacketBuffers *bufs, int MQTTVersion)
	Sends an MQTT packet from multiple buffers in one system call write. More...
int	MQTTPacket_encode (char *buf, size_t length)
	Encodes the message length according to the MQTT algorithm. More...
int	MQTTPacket_decode (networkHandles *net, size_t *value)
	Decodes the message length according to the MQTT algorithm. More...
int	readInt (char **pptr)
	Calculates an integer from two bytes read from the input buffer. More...
char *	readUTF (char **pptr, char *enddata)
	Reads a "UTF" string from the input buffer. More...
unsigned char	readChar (char **pptr)
	Reads one character from the input buffer. More...
void	writeChar (char **pptr, char c)
	Writes one character to an output buffer. More...
void	writeInt (char **pptr, int anInt)
	Writes an integer as 2 bytes to an output buffer. More...
void	writeUTF (char **pptr, const char *string)
	Writes a "UTF" string to an output buffer. More...
void	writeData (char **pptr, const void *data, int datalen)
	Writes length delimited data to an output buffer. More...
void *	MQTTPacket_header_only (int MQTTVersion, unsigned char aHeader, char *data, size_t datalen)
	Function used in the new packets table to create packets which have only a header. More...
int	MQTTPacket_send_disconnect (Clients *client, enum MQTTReasonCodes reason, MQTTProperties *props)
	Send an MQTT disconnect packet down a socket. More...
void *	MQTTPacket_publish (int MQTTVersion, unsigned char aHeader, char *data, size_t datalen)
	Function used in the new packets table to create publish packets. More...
void	MQTTPacket_freePublish (Publish *pack)
	Free allocated storage for a publish packet. More...
void	MQTTPacket_freeAck (Ack *pack)
	Free allocated storage for an ack packet. More...
int	MQTTPacket_send_puback (int MQTTVersion, int msgid, networkHandles *net, const char *clientID)
	Send an MQTT PUBACK packet down a socket. More...
void	MQTTPacket_freeSuback (Suback *pack)
	Free allocated storage for a suback packet. More...
void	MQTTPacket_freeUnsuback (Unsuback *pack)
	Free allocated storage for a suback packet. More...
int	MQTTPacket_send_pubrec (int MQTTVersion, int msgid, networkHandles *net, const char *clientID)
	Send an MQTT PUBREC packet down a socket. More...
int	MQTTPacket_send_pubrel (int MQTTVersion, int msgid, int dup, networkHandles *net, const char *clientID)
	Send an MQTT PUBREL packet down a socket. More...
int	MQTTPacket_send_pubcomp (int MQTTVersion, int msgid, networkHandles *net, const char *clientID)
	Send an MQTT PUBCOMP packet down a socket. More...
void *	MQTTPacket_ack (int MQTTVersion, unsigned char aHeader, char *data, size_t datalen)
	Function used in the new packets table to create acknowledgement packets. More...
int	MQTTPacket_send_publish (Publish *pack, int dup, int qos, int retained, networkHandles *net, const char *clientID)
	Send an MQTT PUBLISH packet down a socket. More...
void	MQTTPacket_free_packet (MQTTPacket *pack)
	Free allocated storage for a various packet tyoes. More...
void	writeInt4 (char **pptr, int anInt)
	Writes an integer as 4 bytes to an output buffer. More...
int	readInt4 (char **pptr)
	Calculates an integer from two bytes read from the input buffer. More...
void	writeMQTTLenString (char **pptr, MQTTLenString lenstring)
int	MQTTLenStringRead (MQTTLenString *lenstring, char **pptr, char *enddata)
int	MQTTPacket_VBIlen (int rem_len)
int	MQTTPacket_VBIdecode (int(*getcharfn)(char *, int), unsigned int *value)
	Decodes the message length according to the MQTT algorithm. More...
int	bufchar (char *c, int count)
int	MQTTPacket_decodeBuf (char *buf, unsigned int *value)

Variables
static const char *	packet_names []
	List of the predefined MQTT v3/v5 packet names. More...
const char **	MQTTClient_packet_names = packet_names
pf	new_packets []
	Array of functions to build packets, indexed according to packet code. More...
static char *	bufptr

Detailed Description

functions to deal with reading and writing of MQTT packets from and to sockets

Some other related functions are in the MQTTPacketOut module

Function Documentation

MQTTPacket_ack()

void* MQTTPacket_ack	(	int	MQTTVersion,
		unsigned char	aHeader,
		char *	data,
		size_t	datalen
	)

Function used in the new packets table to create acknowledgement packets.

Parameters

MQTTVersion	the version of MQTT being used
aHeader	the MQTT header byte
data	the rest of the packet
datalen	the length of the rest of the packet

Returns

pointer to the packet structure

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MQTTPacket_decode()

int MQTTPacket_decode	(	networkHandles *	net,
		size_t *	value
	)

Decodes the message length according to the MQTT algorithm.

Parameters

socket	the socket from which to read the bytes
value	the decoded length returned

Returns

the number of bytes read from the socket

MQTTPacket_encode()

int MQTTPacket_encode	(	char *	buf,
		size_t	length
	)

Encodes the message length according to the MQTT algorithm.

Parameters

buf	the buffer into which the encoded data is written
length	the length to be encoded

Returns

the number of bytes written to buffer

MQTTPacket_Factory()

void* MQTTPacket_Factory	(	int	MQTTVersion,
		networkHandles *	net,
		int *	error
	)

Reads one MQTT packet from a socket.

Parameters

socket	a socket from which to read an MQTT packet
error	pointer to the error code which is completed if no packet is returned

Returns

the packet structure or NULL if there was an error

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MQTTPacket_free_packet()

void MQTTPacket_free_packet

(

MQTTPacket *

pack

)

Free allocated storage for a various packet tyoes.

Parameters

pack	pointer to the suback packet structure

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MQTTPacket_freeAck()

void MQTTPacket_freeAck

(

Ack *

pack

)

Free allocated storage for an ack packet.

Parameters

pack	pointer to the publish packet structure

MQTTPacket_freePublish()

void MQTTPacket_freePublish

(

Publish *

pack

)

Free allocated storage for a publish packet.

Parameters

pack	pointer to the publish packet structure

MQTTPacket_freeSuback()

void MQTTPacket_freeSuback

(

Suback *

pack

)

Free allocated storage for a suback packet.

Parameters

pack	pointer to the suback packet structure

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MQTTPacket_freeUnsuback()

void MQTTPacket_freeUnsuback

(

Unsuback *

pack

)

Free allocated storage for a suback packet.

Parameters

pack	pointer to the suback packet structure

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MQTTPacket_header_only()

void* MQTTPacket_header_only	(	int	MQTTVersion,
		unsigned char	aHeader,
		char *	data,
		size_t	datalen
	)

Function used in the new packets table to create packets which have only a header.

Parameters

MQTTVersion	the version of MQTT
aHeader	the MQTT header byte
data	the rest of the packet
datalen	the length of the rest of the packet

Returns

pointer to the packet structure

MQTTPacket_name()

const char* MQTTPacket_name

(

int

ptype

)

Converts an MQTT packet code into its name.

Parameters

ptype

packet code

Returns

the corresponding string, or "UNKNOWN"

MQTTPacket_publish()

void* MQTTPacket_publish	(	int	MQTTVersion,
		unsigned char	aHeader,
		char *	data,
		size_t	datalen
	)

Function used in the new packets table to create publish packets.

Parameters

MQTTVersion
aHeader	the MQTT header byte
data	the rest of the packet
datalen	the length of the rest of the packet

Returns

pointer to the packet structure

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MQTTPacket_send()

int MQTTPacket_send	(	networkHandles *	net,
		Header	header,
		char *	buffer,
		size_t	buflen,
		int	freeData,
		int	MQTTVersion
	)

Sends an MQTT packet in one system call write.

Parameters

socket	the socket to which to write the data
header	the one-byte MQTT header
buffer	the rest of the buffer to write (not including remaining length)
buflen	the length of the data in buffer to be written
MQTTVersion	the version of MQTT being used

Returns

the completion code (TCPSOCKET_COMPLETE etc)

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MQTTPacket_send_ack()

static int MQTTPacket_send_ack ( int  MQTTVersion, int  type, int  msgid, int  dup, networkHandles *  net  )

static

Send an MQTT acknowledgement packet down a socket.

Parameters

MQTTVersion	the version of MQTT being used
type	the MQTT packet type e.g. SUBACK
msgid	the MQTT message id to use
dup	boolean - whether to set the MQTT DUP flag
net	the network handle to send the data to

Returns

the completion code (e.g. TCPSOCKET_COMPLETE)

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MQTTPacket_send_disconnect()

int MQTTPacket_send_disconnect	(	Clients *	client,
		enum MQTTReasonCodes	reason,
		MQTTProperties *	props
	)

Send an MQTT disconnect packet down a socket.

Parameters

socket

the open socket to send the data to

Returns

the completion code (e.g. TCPSOCKET_COMPLETE)

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MQTTPacket_send_puback()

int MQTTPacket_send_puback	(	int	MQTTVersion,
		int	msgid,
		networkHandles *	net,
		const char *	clientID
	)

Send an MQTT PUBACK packet down a socket.

Parameters

MQTTVersion	the version of MQTT being used
msgid	the MQTT message id to use
socket	the open socket to send the data to
clientID	the string client identifier, only used for tracing

Returns

the completion code (e.g. TCPSOCKET_COMPLETE)

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MQTTPacket_send_pubcomp()

int MQTTPacket_send_pubcomp	(	int	MQTTVersion,
		int	msgid,
		networkHandles *	net,
		const char *	clientID
	)

Send an MQTT PUBCOMP packet down a socket.

Parameters

MQTTVersion	the version of MQTT being used
msgid	the MQTT message id to use
socket	the open socket to send the data to
clientID	the string client identifier, only used for tracing

Returns

the completion code (e.g. TCPSOCKET_COMPLETE)

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MQTTPacket_send_publish()

int MQTTPacket_send_publish	(	Publish *	pack,
		int	dup,
		int	qos,
		int	retained,
		networkHandles *	net,
		const char *	clientID
	)

Send an MQTT PUBLISH packet down a socket.

Parameters

pack	a structure from which to get some values to use, e.g topic, payload
dup	boolean - whether to set the MQTT DUP flag
qos	the value to use for the MQTT QoS setting
retained	boolean - whether to set the MQTT retained flag
socket	the open socket to send the data to
clientID	the string client identifier, only used for tracing

Returns

the completion code (e.g. TCPSOCKET_COMPLETE)

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MQTTPacket_send_pubrec()

int MQTTPacket_send_pubrec	(	int	MQTTVersion,
		int	msgid,
		networkHandles *	net,
		const char *	clientID
	)

Send an MQTT PUBREC packet down a socket.

Parameters

MQTTVersion	the version of MQTT being used
msgid	the MQTT message id to use
socket	the open socket to send the data to
clientID	the string client identifier, only used for tracing

Returns

the completion code (e.g. TCPSOCKET_COMPLETE)

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MQTTPacket_send_pubrel()

int MQTTPacket_send_pubrel	(	int	MQTTVersion,
		int	msgid,
		int	dup,
		networkHandles *	net,
		const char *	clientID
	)

Send an MQTT PUBREL packet down a socket.

Parameters

MQTTVersion	the version of MQTT being used
msgid	the MQTT message id to use
dup	boolean - whether to set the MQTT DUP flag
socket	the open socket to send the data to
clientID	the string client identifier, only used for tracing

Returns

the completion code (e.g. TCPSOCKET_COMPLETE)

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MQTTPacket_sends()

int MQTTPacket_sends	(	networkHandles *	net,
		Header	header,
		PacketBuffers *	bufs,
		int	MQTTVersion
	)

Sends an MQTT packet from multiple buffers in one system call write.

Parameters

socket	the socket to which to write the data
header	the one-byte MQTT header
count	the number of buffers
buffers	the rest of the buffers to write (not including remaining length)
buflens	the lengths of the data in the array of buffers to be written
the	MQTT version being used

Returns

the completion code (TCPSOCKET_COMPLETE etc)

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MQTTPacket_VBIdecode()

int MQTTPacket_VBIdecode	(	int(*)(char *, int)	getcharfn,
		unsigned int *	value
	)

Decodes the message length according to the MQTT algorithm.

Parameters

getcharfn	pointer to function to read the next character from the data source
value	the decoded length returned

Returns

the number of bytes read from the socket

readChar()

unsigned char readChar

(

char **

pptr

)

Reads one character from the input buffer.

Parameters

pptr	pointer to the input buffer - incremented by the number of bytes used & returned

Returns

the character read

readInt()

int readInt

(

char **

pptr

)

Calculates an integer from two bytes read from the input buffer.

Parameters

pptr	pointer to the input buffer - incremented by the number of bytes used & returned

Returns

the integer value calculated

readInt4()

int readInt4

(

char **

pptr

)

Calculates an integer from two bytes read from the input buffer.

Parameters

pptr	pointer to the input buffer - incremented by the number of bytes used & returned

Returns

the integer value calculated

readUTF()

char* readUTF	(	char **	pptr,
		char *	enddata
	)

Reads a "UTF" string from the input buffer.

UTF as in the MQTT v3 spec which really means a length delimited string. So it reads the two byte length then the data according to that length. The end of the buffer is provided too, so we can prevent buffer overruns caused by an incorrect length.

Parameters

pptr	pointer to the input buffer - incremented by the number of bytes used & returned
enddata	pointer to the end of the buffer not to be read beyond

Returns

an allocated C string holding the characters read, or NULL if the length read would have caused an overrun.

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readUTFlen()

static char * readUTFlen ( char **  pptr, char *  enddata, int *  len  )

static

Reads a "UTF" string from the input buffer.

UTF as in the MQTT v3 spec which really means a length delimited string. So it reads the two byte length then the data according to that length. The end of the buffer is provided too, so we can prevent buffer overruns caused by an incorrect length.

Parameters

pptr	pointer to the input buffer - incremented by the number of bytes used & returned
enddata	pointer to the end of the buffer not to be read beyond
len	returns the calculcated value of the length bytes read

Returns

an allocated C string holding the characters read, or NULL if the length read would have caused an overrun.

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writeChar()

void writeChar	(	char **	pptr,
		char	c
	)

Writes one character to an output buffer.

Parameters

pptr	pointer to the output buffer - incremented by the number of bytes used & returned
c	the character to write

writeData()

void writeData	(	char **	pptr,
		const void *	data,
		int	datalen
	)

Writes length delimited data to an output buffer.

Parameters

pptr	pointer to the output buffer - incremented by the number of bytes used & returned
data	the data to write
datalen	the length of the data to write

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writeInt()

void writeInt	(	char **	pptr,
		int	anInt
	)

Writes an integer as 2 bytes to an output buffer.

Parameters

pptr	pointer to the output buffer - incremented by the number of bytes used & returned
anInt	the integer to write

writeInt4()

void writeInt4	(	char **	pptr,
		int	anInt
	)

Writes an integer as 4 bytes to an output buffer.

Parameters

pptr	pointer to the output buffer - incremented by the number of bytes used & returned
anInt	the integer to write

writeUTF()

void writeUTF	(	char **	pptr,
		const char *	string
	)

Writes a "UTF" string to an output buffer.

Converts C string to length-delimited.

Parameters

pptr	pointer to the output buffer - incremented by the number of bytes used & returned
string	the C string to write

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Variable Documentation

new_packets

pf new_packets[]

Initial value:

=
{
        NULL,   
        NULL,   
        MQTTPacket_connack, 
        MQTTPacket_publish,     
        MQTTPacket_ack, 
        MQTTPacket_ack, 
        MQTTPacket_ack, 
        MQTTPacket_ack, 
        NULL, 
        MQTTPacket_suback, 
        NULL, 
        MQTTPacket_unsuback, 
        MQTTPacket_header_only, 
        MQTTPacket_header_only, 
        MQTTPacket_ack,  
        MQTTPacket_ack   
}

Array of functions to build packets, indexed according to packet code.

packet_names

const char* packet_names[]

static

Initial value:

=
{
        "RESERVED", "CONNECT", "CONNACK", "PUBLISH", "PUBACK", "PUBREC", "PUBREL",
        "PUBCOMP", "SUBSCRIBE", "SUBACK", "UNSUBSCRIBE", "UNSUBACK",
        "PINGREQ", "PINGRESP", "DISCONNECT", "AUTH"
}

List of the predefined MQTT v3/v5 packet names.