The getzmqnotifications RPC returns information about the active ZeroMQ notifications.
getzmqnotifications none
*bitcoin-cli help getzmqnotifications
getzmqnotifications Returns information about the active ZeroMQ notifications. Result: [ (json array) { (json object) "type" : "str", (string) Type of notification "address" : "str", (string) Address of the publisher "hwm" : n (numeric) Outbound message high water mark }, ... ] Examples: > bitcoin-cli getzmqnotifications > curl --user myusername --data-binary '{"jsonrpc": "1.0", "id": "curltest", "method": "getzmqnotifications", "params": []}' -H 'content-type: text/plain;' http://127.0.0.1:8332/