You can use the default property to specify a default server in the server-list section. Valid values are true and false.
The following JSON configuration file example shows a default server.
"broker_list": "{\"settings\": {\"server-list\": [{\"server\": \"123.456.1.1\",\"description\": \"View Server 1\",\"default\": true,\"username\": \"User1\",\"domain\": \"TestDomain1\"}]}}" }