Reference

Reference Contents:

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 and VME controller statistics.

  • 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.