CDK Error: Connection refused; X Dev API, mysqlconnector8 (no replies)

I have mysqlxsys installed on my MySQL Server 5.7. I have created the world_x sample schema, along with the sample city, country, etc. tables. My user@hostname has all privileges on the tables. I can execute queries on the tables with MySQLWorkbench. and with mysqlsh. I downloaded and built mysql-connector-cpp-master. The install created libmysqlcppconn8.so. I've linked and compiled a test app against this library. When I try to establish a Session I get the error

terminate called after throwing an instance of 'mysqlx::Error'
what(): CDK Error: Connection refused (generic:111)
Can you tell me what's going on?

I previously built and successfully tested mysqlcppconn from mysql-connector-c++-1.1.9.
The X Dev API docs mention that mysqlcppconn2 will be built. Have I installed the wrong source?

thanks