Return the port number of a `sparklyr` backend.
Source:R/connection_spark.R
sparklyr_get_backend_port.RdRetrieve the port number of the `sparklyr` backend associated with a Spark connection.
R/connection_spark.R
sparklyr_get_backend_port.RdRetrieve the port number of the `sparklyr` backend associated with a Spark connection.