Skip to content
Start free evaluation

pdcomm::modbus::QtEndpoint

Class

Modbus endpoint that takes a QJsonObject command and returns the result object of the reply.

class QtEndpoint

Construction creates a disconnected endpoint with the default configuration and throws std::runtime_error if the library cannot create it. The object is movable but not copyable.

Write holding register 0 in the local data model, as the MFC consumer examples/modbus-mfc/main.cpp does:

#include <QJsonArray>
// ...
pdcomm::modbus::QtEndpoint endpoint;
const QJsonObject result = endpoint.call(
    QJsonObject{{"action", "execute"}, {"pdu", QJsonArray{6, 0, 0, 0, 9}}});
// result: {"response":[6,0,0,0,9],"source":"local","status":"success"}

Notes

  • A client request or connect blocks until the response, the connection or the configured timeout. Run such commands in a worker thread (for example a QThread that owns the endpoint) and hand the results to the GUI thread with a queued signal; never block the GUI thread. A server or gateway answers requests only while that worker sends {"action":"poll"} regularly.

Members

call

Method

Runs one JSON command and returns its result object.

QJsonObject call(const QJsonObject &command)

The command is serialized as compact UTF-8 JSON and passed to Endpoint::call(); see pdcomm_modbus_call() for the command set.

Parameters

NameDescription
commandCommand object with an action member.

Returns

The result member of the {"ok":true,"result":...} reply.

Notes

  • Throws std::runtime_error: whose what() is the error reply {"error":"...","ok":false} when the command fails, or a fixed text when the library call itself fails.

Privacy Policy