LWM2M with DTLS and PSK

[sonny82]

Hi,

I'm trying to use LWM2M plugin with DTLS and PSK in version 4.3.7 but without any success.
In emqx.conf I commented out listener.ssl.external.ciphers and uncommented listener.ssl.external.psk_ciphers.
I enabled the emqx_psk_file plugin.
In psk.txt file I entered my client id and key (myclientId:C127D993068150012D74863733313864F26932C7E707E724A479BBA730580538).
In emqx_lwm2m.conf I commented out lwm2m.dtls.ciphers and uncommented lwm2m.dtls.psk_ciphers.
Then I restarted EMQX.

Now if I try to connect using leshan client I get the following exception:

2021-08-27 16:29:51,735 INFO LeshanClientDemo - DTLS Full Handshake initiated by client : STARTED ...
2021-08-27 16:29:51,750 INFO DefaultRegistrationEngine - Unable to send register request : Received 'fatal alert/INSUFFICIENT_SECURITY'
2021-08-27 16:29:51,750 INFO LeshanClientDemo - DTLS Full Handshake initiated by client : FAILED (Received 'fatal alert/INSUFFICIENT_SECURITY')

Leshan client command that I use:
java -jar .\leshan-client-demo.jar -n myclientId -u localhost:5684 -i myclientId -p C127D993068150012D74863733313864F26932C7E707E724A479BBA730580538

In the log file I can see:

2021-08-27T16:44:04.480000+02:00 [notice] DTLS server: In state hello at dtls_handshake.erl:194 generated SERVER ALERT: Fatal - Insufficient Security
2021-08-27T16:44:04.480000+02:00 [error] supervisor: 'esockd_connection_sup - <0.442.0>', errorContext: connection_shutdown, reason: {ssl_error,{tls_alert,{insufficient_security,"DTLS server: In state hello at dtls_handshake.erl:194 generated SERVER ALERT: Fatal - Insufficient Security\n"}}}, offender: [{pid,<0.1333.0>},{name,connection},{mfargs,{lwm2m_coap_channel,start_link,[[{lifetime_max,86400},{lifetime_min,1},{mountpoint,<<"lwm2m/%e/">>},{port,5683},{auto_observe,false},{qmode_time_window,0},{update_msg_publish_condition,contains_object_list},{topics,[...]}]]}}]

Could you please help me, I don't find any more help in the docu..

Thank you in advance and best regards,
Sonny