mqtt_demo

flutter mqtt demo

doc : https://juejin.im/post/6844903985460019213

相关错误：

Unhandled Exception: FileSystemException: Cannot open file, path = '...' 
(OS Error: No such file or directory, errno = 2)

TlsException: Failure trusting builtin roots

SocketException: OS Error: Connection reset by peer, errno = 104