How can I send a broadcast message in Delphi

问题

I want to send a broadcast UDP message in my LAN, the application is client/server.

I desire to update the user interface, this way any computer send a message to update the others. Can I use UDPServer indy, how to use ? Thanks

回答1:

Create two applications, one represents the sender and the other the receiver.

Sender

Drop a TIdUDPClient and a TButton component on your form. On the OnClick handler of the button write:

procedure TfrmUDPClient.BroadcastClick(Sender: TObject);
begin
  UDPClient.Broadcast('Test', 8090);
end;

Receiver

Drop a TIdUDPServer on your form, define the same port (8090) for it and add this to the OnUDPRead handler:

procedure TfrmUDPServer.UDPServerUDPRead(Sender: TObject; AData: TStream; ABinding: TIdSocketHandle);
var
  DataStringStream: TStringStream;
  Msg: String;
begin
  DataStringStream := TStringStream.Create('');
  try
    DataStringStream.CopyFrom(AData, AData.Size);
    Msg := DataStringStream.DataString;
  finally
    DataStringStream.Free;
  end;
  ShowMessage(Msg);
end;

Or, in later versions of Indy:

procedure TfrmUDPServer.UDPServerUDPRead(AThread: TIdUDPListenerThread;
  const AData: TIdBytes; ABinding: TIdSocketHandle);
var
  Msg: String;
begin
  try
    {if you actually sent a string encoded in utf-8}
    Msg := TEncoding.UTF8.GetString(AData);
  except
  end;

  ShowMessage(Msg);
end;

To test, run both applications and click on the button. To test with two or more "listeners" you have to use another machine. That is, you can't run multiple listeners on the same IP.

回答2:

Create a TIdUDPServer or TIdUDPClient component. Both have Broadcast methods that should do exactly what you need.

来源：https://stackoverflow.com/questions/3480729/how-can-i-send-a-broadcast-message-in-delphi