Sending UDP packets via the internet and between processes?

[EHuckert]

On Saturday, 12 May 2018 at 09:29:43 UTC, Dustin Keeting wrote:
> I'm setting up two applications, a client and a server, that 
> will exchange some data back and forth. The server may be on 
> the same machine as the client, or it may not be, or there 
> might be multiple clients which may or may not be on the same 
> machine. Both applications will be running other code and I'd 
> like them to be able to access a list of received packets 
> rather than waiting for them to come in.
>
> What do I need to do to set this up? This is as far as I've got:
>
>         ushort port = 3000;
>
> 	auto sender = new UdpSocket();
> 	sender.blocking = false;
> 	auto address = new InternetAddress(port);
> 	sender.bind(address);
>
> 	ubyte[Packet.sizeof] bytes;
> 	Packet* packet = cast(Packet*)bytes.ptr;
>         //not sure how to convert a struct to big endian easily?
>
> 	sender.send(bytes);
>
> I'm not really sure how to receive sent bytes or if I need to 
> put in ip addresses to make it work online? I've looked at a 
> couple of examples and I've gotten some html to work by 
> accessing a localhost port, but I've always struggled with 
> networking, so if someone can help explain how I'm meant to 
> connect sockets that may be online or on the same machine... 
> that would be a big help!

You may look at my Web page 
http://www.huckert.com/ehuckert/huckertp112.html under
the heading "Sockets". You will find there a working UDP sender 
(a client) and
a working receiver (a server). Both programs are written in D. I 
use UDP heavily for
logging. For the communication between two processes on the same 
machine I would rather recommend TCP instead of UDP. To connect 
sockets on the same machine it
is normally sufficient to use "localhost" as the hostname or 
"127.0.0.1". From time
to time I encounter a small problem: the firewalls on the 
machines may block the communication on the ports. For tests I 
prefer switching off the firewalls.

E.Huckert