The JSON-RPC service needs to be enabled and set the port in the node configuration file. If not configured, the service is disable by default.
How to enable or disable JSON-RPC service of a node
Add below items in node's configuration file, then enable or disable it:
node.jsonrpc {
httpFullNodeEnable = true
httpFullNodePort = 50545
httpSolidityEnable = true
httpSolidityPort = 50555
}