src/platform/net/srp.h File Reference

SRP or Simple Retransmission Protocol is a protocol which retransmits packets if they have not been confirmed within a predefined time. More...

#include <stdint.h>
#include <stdbool.h>
#include "net/net.h"

Go to the source code of this file.

Data Structures
struct	SrpHeader
	Header used by SRP protocol. More...
Defines
#define	SRP_MAX_SIZE   512
	Maximum size of one SRP message.
#define	SRP_TX_QUEUE_SIZE   ( SRP_MAX_SIZE * 4 )
	Transmit queue buffer size.
#define	SRP_TX_MAX_QUEUE   8
#define	SRP_RESEND_TIMEOUT   250
	Timeout in milliseconds.
#define	SRP_RESEND_MAX   16
	Max number of resends.
#define	SRP_RX_MAX_CACHE   16
	Max receive confirms.
#define	SRP_FLG_MSG   BIT(0)
	Contains message.
#define	SRP_FLG_BROADCAST   BIT(1)
	Is broadcast (for future usage).
#define	SRP_FLG_ACK_SHIFT   4
	Shift for the number of acks.
#define	SRP_FLG_ACK_MASK   0x30
	Mask for the number of acks.
#define	SRP_MAX_PAYLOAD   ( SRP_MAX_SIZE - sizeof(SrpHeader) )
	maximum size of the payload of a SRP message.
#define	SRP_MAX_ACKS   2
	Maximum number of acknowledges.
Functions
void	_srpUdpTx (SockAddr *txAddr, uint8_t *udpPayload, int len)
	Transmit UDP packet.
void	_srpRx (SockAddr *rxAddr, uint8_t *message, int len)
	Process a received SRP packet.
void	srpInit ()
	Initializes the SRP protocol engine.
void	srpUdpRx (SockAddr *rxAddr, uint8_t *udpPayload, int len)
	Invoked by UDP stack for receiving a SRP packet.
bool	srpTx (SockAddr *txAddr, uint8_t *message, int len)
	Invoked by application for sending an SRP packet.
void	srpProcess ()
	Should be called periodically to process any pending requests.

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Detailed Description

SRP or Simple Retransmission Protocol is a protocol which retransmits packets if they have not been confirmed within a predefined time.

When a packet is lost, i.e. it has not been confirmed within a certain time, after multiple sends, it will notify the sender that the packet did not make it.

SRP is an asynchronous protocol, multiple packets may be in processing, being send but not confirmed. when replying the acknowledge of the sender may be in the receiving packets.

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Define Documentation

#define SRP_FLG_BROADCAST   BIT(1)

Is broadcast (for future usage).

#define SRP_MAX_ACKS   2

Maximum number of acknowledges.

#define SRP_MAX_SIZE   512

Maximum size of one SRP message.

#define SRP_TX_QUEUE_SIZE   ( SRP_MAX_SIZE * 4 )

Transmit queue buffer size.

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Function Documentation

void _srpRx	(	SockAddr *	addr,
		uint8_t *	message,
		int	len
	)

Process a received SRP packet.

Invoked by SRP when a SRP packet has been received.

This is a callback and must be implemented by the protocol stack.

Note:

Implementors should take care not to do too much in this call. Executing long running processes will stall SRP processing. Complecated tasks should be executed outside of this function.

Parameters:

	rxAddr	The address of the sender.
	message	The message to parse.
	len	The length of the message.

void _srpUdpTx	(	SockAddr *	txAddr,
		uint8_t *	udpPayload,
		int	len
	)

Transmit UDP packet.

Invoked by SRP when its done formatting a packet.

This is a callback and must be implemented by the protocol stack.

Parameters:

	txAddr	The addresss to send to.
	udpPayload	The payload to transmit.
	len	The length of the payload.

bool srpTx	(	SockAddr *	txAddr,
		uint8_t *	message,
		int	len
	)

Invoked by application for sending an SRP packet.

Note:

SRP packets may be no longer than SRP_MAX_PAYLOAD.

Parameters:

	txIpAddr	The ip address to send to.
	message	The message to send.
	len	The length of the message.

void srpUdpRx	(	SockAddr *	rxAddr,
		uint8_t *	udpPayload,
		int	len
	)

Invoked by UDP stack for receiving a SRP packet.

Parameters:

	rxAddr	The sender address.
	udpPayload	The data in the udp packet.
	len	The lenght of the payload.