Reference¶

JSON-RPC remote control support¶

MVME uses the JSON-RPC specification to implement basic remote control functionality. To enable/disable the RPC-Server use the “Workspace Settings” button in the DAQ Controls Window and follow the instructions there.

If the RPC-Server is enabled mvme will open a TCP listening socket and accept incoming connections. By default mvme binds to all interfaces and listens on port 13800.

Requests are currently not length-prefixed, instead data is read until a full JSON object has been received. The received JSON is then interpreted according to the JSON-RPC spec.

Note: The JSON-RPC batch feature is not supported by the server implementation.

A command line client written in Python3 can be found in the mvme distribution under extras/mvme_jsonrpc_client.py:

$ python3 extras/mvme_jsonrpc_client.py localhost 13800 getDAQState
---> {"id": "0", "jsonrpc": "2.0", "method": "getDAQState", "params": []}
<--- {"id": "0", "jsonrpc": "2.0", "result": "Running"}

Examples¶

Requesting DAQ State:

---> {"id": "0", "jsonrpc": "2.0", "method": "getDAQState", "params": []}
<--- {"id": "0", "jsonrpc": "2.0", "result": "Running"}

Starting data acquisition:

---> {"id": "0", "jsonrpc": "2.0", "method": "startDAQ", "params": []}
<--- {"id": "0", "jsonrpc": "2.0", "result": true}

An error response:

---> {"id": "0", "jsonrpc": "2.0", "method": "startDAQ", "params": []}
<--- {"error": {"code": 102, "message": "DAQ readout worker busy"}, "id": "0", "jsonrpc": "2.0"}

Requesting DAQ stats:

---> {"id": "0", "jsonrpc": "2.0", "method": "getDAQStats", "params": []}
<--- {"id": "0", "jsonrpc": "2.0", "result": {"analysisEfficiency": 1, "analyzedBuffers": 4644, "buffersWithErrors": 0, "currentTime": "2018-06-14T11:45:21", "droppedBuffers": 0, "endTime": null, "listFileBytesWritten": 0, "listFileFilename": "", "runId": "180614_114412", "startTime": "2018-06-14T11:44:13", "state": "Running", "totalBuffersRead": 4644, "totalBytesRead": 6366924, "totalNetBytesRead": 5851300}}

Methods¶

getVersion¶

Returns the version of MVME running the JSON RPC services.

Parameters

None
Returns

String containing version information.

getLogMessages¶

Returns the messages buffered up in the MVME log.

Parameters

None
Returns

StringList - List containing the log messages from oldest to newest.

getDAQStats¶

Returns information about the current DAQ run including counter values, the current run ID, listfile output filename and start time.

Parameters

None
Returns

Object

getVMEControllerType¶

Returns the type of VME controller in use.

Parameters

None
Returns

String

getVMEControllerStats¶

Returns detailed VME controller statistics if available for the current controller type.

Parameters

None
Returns:

Object

getVMEControllerState¶

Returns the connection state of the VME controller.

Parameters

None
Returns:

String - “Connected”, “Disconnected” or “Connecting”

reconnectVMEController¶

Starts a reconnection attempt of the VME controller. The operation is asynchronous, thus the result will not be directly available. Instead the controller state needs to be polled via getVMEControllerState to see the result of the reconnection attempt.

Note: this might in the future be changed to a synchronous version, which immediately returns the result or any errors that occured.

Parameters

None
Returns:

String - “Reconnection attempt initiated”

getDAQState¶

Returns the current state of the DAQ.

Parameters

None
Returns String - “Idle”, “Starting”, “Running”, “Stopping” or “Paused”

startDAQ¶

Starts a new DAQ run. The system must be idle, meaning any previous DAQ runs must have been stopped.

Parameters

None
Returns

true on success, error status and additional information otherwise.

stopDAQ¶

Stops the current DAQ run.

Parameters

None
Returns

true on success, error status and additional information otherwise.