YOUSEFUL / DELPHI / COMPONENTS

All Atlas MQTT components · Atlas MQTT guide

EAtlasMqttError

Base class of every Atlas MQTT exception; raised for invalid arguments, settings and packets.

Class Unit Atlas.MqttCodec · Inherits Exception · Product Atlas MQTT

Description

Raised directly for mistakes the caller can fix, for example:

• an invalid topic or filter;
• Host missing, or an empty ClientId without CleanSession;
• KeepAlive or MaxInFlight out of range;
• quality 0 published while not connected;
• the in-flight limit reached;
• a packet TAtlasMqttCodec.Encode cannot encode.

Descendants: EAtlasMqttProtocolError for malformed input, and EAtlasMqttTransportError for socket failures. Catch EAtlasMqttError to catch them all. Declared in Atlas.MqttCodec. Connection problems inside the client are not raised; they arrive through OnDisconnected and OnError.

This type has no members of its own beyond those listed in its description.

Examples

uses
  System.SysUtils, Atlas.MqttCodec, Atlas.MqttClient;

function TryPublish(Client: TAtlasMqttClient; const Topic, Text: string): Boolean;
begin
  try
    Client.Publish(Topic, Text, qosAtLeastOnce);
    Result := True;
  except
    on EAtlasMqttError do  // an invalid topic, or MaxInFlight messages already waiting
      Result := False;
  end;
end;

Related

EAtlasMqttProtocolError · EAtlasMqttTransportError

Also in Atlas MQTT

TAtlasMqttClient · TAtlasMqttBroker