logback-config.xml

<configuration>
        <appender name="STDOUT" class="ch.qos.logback.core.ConsoleAppender">
                <encoder>
                        <pattern>%d %p %C{0} - %m%n</pattern>
                </encoder>
        </appender>

        <root level="WARN">
                <appender-ref ref="STDOUT" />
        </root>

        <logger name="org.eclipse.leshan" level="DEBUG"/><!-- default value is INFO -->
        <logger name="org.eclipse.leshan.server.security.SecurityCheck" level="DEBUG"/>
        <logger name="org.eclipse.leshan.core.model.LwM2mModel" level="TRACE"/>

        <!-- All above is the default config, the line below is to search something in DTLS stack -->
        <logger name="org.eclipse.californium" level="DEBUG"/>
</configuration>