TLS handshake in aws_iot_connect() function

Question

Hi, 
 
 Currently we working on a project that uses: 
 
 nRF9160 
 Zyphre OS 
 Segger Embedded Studio for Arm (Nordic Edition) V4.52 
 SDK v1.3

CONFIG_MQTT_LIB_TLS

In nRF Connect SDK - AWS IoT it mentions that the TLS handshake is performed in the aws_iot_connect () function, specifically in the following note: 
 
 After a thorough review we have not found where the TLS handshake is do it, We think the TLS handshake is doing in some of these functions (zephyr\subsys
et\lib\mqtt\mqtt.c):

mqtt_transport_connect(client); 
 connect_request_encode(client, &packet); 
 mqtt_transport_write(client, packet.cur,packet.end - packet.cur);

Could someone from your team tell us where is the TLS handshake inside the aws_iot_connect () ? 
 
 Thanks a lot, 
 René D.

Didrik Rokhaug · Accepted Answer

A TLS handshake will be done if you call connect() on a TLS socket. 
 A TLS socket is created by calling socket(sa_family, SOCK_STREAM, IPPROTO_TLS_1_2) , where sa_family is the IP version ( AF_INET for IPv4 or AF_INET6 for IPv6)

TLS handshake in aws_iot_connect() function

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