Bitcoin ZeroMQ and Scala application
It is not specified what to subscribe.

socket.connect("tcp://127.0.0.1:28332")

socket.subscribe("hashtx");
# if you need raw data or block data, to add-&gt;
socket.subscribe("hashblock");
socket.subscribe("rawblock");
socket.subscribe("rawtx");


see.
https://github.com/bitcoin/bitcoin/blob/master/contrib/zmq/zmq_sub.py