14-STM32+W5500 basic control chapter (self-built IoT platform) – transplant mbedtls to realize STM32+w5500 connect to MQTT server in SSL one-way authentication mode (server certificate is not verified)

In the network communication, if SSL is not added, the information will be exposed in the network communication in clear text. This section transplants the mbedtls library to let W5500 connect to the MQTT server in SSL mode.

First, briefly explain SSL, in fact, the whole is TCP and server communication,
It’s just that after the TCP connection to the server, the encryption method and encryption password are negotiated with the server first.
Then the data is encrypted and transmitted;