Openssl
From Teknologisk videncenter
Debug
Example when debugging a tls connection to mosquitto MQTT broker.
root@beaglebone:/home/debian# openssl s_client -connect 127.0.0.1:8883
CONNECTED(00000003)
Can't use SSL_get_servername
depth=0 C = DK, ST = Denmark, L = Viborg, O = Mercantec, CN = beaglebone.localdomain, emailAddress = heth@mercantec.dk
verify error:num=18:self signed certificate
.....