Iot sdk thesis

Resolving the UNIX dependency:
•
Only Check for matching ifindex, size and remoteIpStr 
Design Decision: 
After adjusting the structure 
session_t, 
only these three variables 
can uniquely identify a session.
Hence, the function reduces to a much simpler form which can be used on Arduino-like boards 
: 
static
inline
int
_dtls_address_equals_impl(
const
session_t *a, 
const
session_t *b)
{ 
if
(a->ifindex != b->ifindex || a->size != b->size ) 
return
0
; 
//Added else for SODAQ
else
{ 
return
strcmp(a->addr.remoteIpStr, b->addr.remoteIpStr); 
} 
} 
Sessions API has been made Arduino-compliant as shown in this section. Now let’s 
move to a more complex - DTLS Connections - API. 
3.3.3
 
DTLS Connections API (dtlsconnection.c, dtlsconnection.h) 
‘DTLS Connections’ API has a structure and multiple functions implemented, that use 
UNIX libraries mentioned above. The structure 
dtls_connection_t 
is used to store the 
information specific to a partifular DTLS connection, has only one UNIX dependency, which 
has been shown in red below: 
typedef
struct
_dtls_connection_t 
{ 
struct
_dtls_connection_t * next; 
int
sock; 
struct
sockaddr_in6 addr
; 
size_t addrLen; 
session_t * dtlsSession; 
lwm2m_object_t * securityObj; 
int
securityInstId; 
lwm2m_context_t * lwm2mH; 
dtls_context_t * dtlsContext; 
time_t lastSend;
} dtls_connection_t; 

---

58 
Resolving the UNIX dependency: 
Similar to 
session_t, 
the UNIX-specific dependencies 
had to be removed and compensated for by a string for IP address, an integer for port and a 
Sodaq_nbIOT object to access the SODAQ NB-IoT API. The SODAQ SARA compatible 
structure has been shown below: 
typedef
struct
_dtls_connection_t 
{ 
struct
_dtls_connection_t * next; 
int
sock;
//struct sockaddr_in6 addr;
//size_t addrLen; //Removed, since it is not required
/*Added for SODAQ Integration*/
Sodaq_nbIOT * nbIOT; 
//Sodaq_nbIOT object to access the SODAQ NB-IoT API
char
* remoteIpStr; 
//To store remote IP address
uint16_t
port; 
//to store remote port
session_t * dtlsSession; 
lwm2m_object_t * securityObj; 
int
securityInstId; 
lwm2m_context_t * lwm2mH; 
dtls_context_t * dtlsContext; 
time_t
lastSend; 
// last time a data was sent to the server (used for NAT 
timeouts)
} dtls_connection_t; 
Now we will see the functions in DTLS Connection API. The most important functions, 
their functionalities and dependencies on UNIX dependencies have been shown below. The 
‘red’ parts indicate UNIX-dependent functions or variables. 
(NOTE: Although every function with socket dependency was studied, adjusted or made 
redundant for making Wakaama with DTLS portable to SODAQ SARA, only a notable few 
have been discussed in this section. The purpose it to give readers a general idea of dependency 
resolution in concise text for better readability.)

---

59 
/* Returns the number sent packets to the address stored in ConnP->addr, or -1 for 
errors */
int
send_data(dtls_connection_t *connP, uint8_t * buffer, size_t length) 
{ 
/* 
*other source lines* 
*/
// sendto() function from sys/socket.h is used to message to connP->addr
nbSent = 
sendto
(connP->sock,
buffer + offset, 
length - offset,
0
, (
struct
sockaddr *)&(connP->addr),
connP->addrLen); 
/*
*other source lines* 
*/
return nbSent; 
}