Lazarus WIN10 LNET UDP local Lan Broadcast
lazarus / 38-Networking and Web Programming

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picstart · 2016-09-08 14:08

The facts
UDP using LNET visual component
local LAN xxx.xxx.xxx.xxx port yyyy
network of esp8266 Iot devices one is broadcasting on xxx.xxx.xxx.255
port yyyy
Other esp8266 IoT devices can receive the broadcast packets
Wireshark on a WIN10 pro can see the broadcast packets the
broadcasting device's  sending port
is 4097
Windows firewall is set to allow project1.exe to run and the port yyyy
is also allowed
Issue
The code displays Connected to xxx.xxx.xxx.255,yyy in Memo1
but fails to get a call back to procedure
TForm1.LUDPComponent1Receive(aSocket: TLSocket);
The error call back is also not called.

Goal
Trying to write the simplest possible code to receive a local lan UDP 
broadcast packet

Maybe the code below is messed up or maybe it is WIN10 and Lazarus and
LNET as the cause.
Any ideas?

Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i unit
Unit1; {$mode objfpc}{$H+} interface uses  Classes, SysUtils,
FileUtil, Forms, Controls, Graphics, Dialogs, StdCtrls, 
lNetComponents, lNet; type   { TForm1 }   TForm1 = class(TForm)   
Button1: TButton;    LUDPComponent1: TLUDPComponent;    Memo1: TMemo; 
  procedure Button1Click(Sender: TObject);    procedure
LUDPComponent1Error(const msg: string; aSocket: TLSocket);   
procedure LUDPComponent1Receive(aSocket: TLSocket);  private    {
private declarations }  public    { public declarations }  end; var 
Form1: TForm1; implementation {$R *.lfm} { TForm1 } procedure
TForm1.LUDPComponent1Error(const msg: string; aSocket:
TLSocket);begin   Memo1.Lines.Add('err'+msg);end; procedure
TForm1.Button1Click(Sender: TObject);begin //LUDPComponent1. if
LUDPComponent1.Connect('xxx.xxx.xxx.255',yyyy) then  Memo1.lines.Add(
'Connected to xxx.xxx.xxx.255,yyy'); end; procedure
TForm1.LUDPComponent1Receive(aSocket: TLSocket);var msg:string;begin 
 Memo1.Lines.Add('>');  LUDPComponent1.GetMessage(msg,aSocket); 
Memo1.lines.Add('recvd='+msg);end; end.

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Thaddy · 2016-09-08 14:52

In general UDP  broadcasts are seldomly allowed on a modern network
without extra configuration, but it should still be possible to use
it.
I'll see if I have a small synapse example available. Windows 10
probably won't work even locally without quite a lot of configuration,
though.

E.g.: IPv6 doesn't allow it at all, just multi-cast.
What are you trying to achieve?

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picstart · 2016-09-08 17:49

First thanks for the reply

FYI a tried synapse and it like LNET didn't work and produced no
errors ..the receive broadcast packet call back was never called.
FYI if I turn off the WIN10 firewall it still will not receive a
broadcast UDP packet.
What am trying to achieve?
It is a small home network using the home router's LAN. The $4 esp8266
Iot devices control relays that replace manual switches. I had it
working with MQTT but it needs a central MQTT 100% uptime server. I
was using a Raspi since I don't want to risk exposure to a web based
MQTT server.
The UDP broadcast allows a esp8266 IoT device to announce its presence
to the other IoT devices. They then can via UDP talk to each other
peer to peer or they can broadcast so all can get the message.
I wanted to bring the Win10 lazarus app into the picture so it could
send commands to change the existing process. ( Ex turn the yard
sprinkler zone 1  on at start time and of at end time)
The lazarus code with its graphic GUI allows for ease of change and
them sends a UDP packet to the esp8266 in charge of the sprinkler to
alter the times etc.
The lazarus code needs to receive local lan broadcasts ( multicast can
cross networks..I may have to use it but it has a broader reach that I
don't need ).
It could be just me but it is unpleasant to think Microsoft knows
better what is best for me and is blocking broadcast UDP.