Re: [liblo] how to connect to a liblo TCP OSC server?

[Stephen S. <rad...@gm...>]

Ah right,  you do make a good point ;)

I believe the terminology choice in this case stems from "device accepting
connections"  (like an HTTP server), as opposed to "device requesting
connections" (like an HTTP client).  I can try to clarify that in the docs,
thanks.

regards,
Steve


On Wed, Aug 5, 2020 at 5:59 PM Aigner Roland <rol...@fh...>
wrote:

> Hi Steve,
>
>
>
> Thanks for your detailed reply, that did indeed help. The cause for
> confusion is in fact terminology and what I would associate with the term
> “server” (i.e. a device providing data) and that the notation is apparently
> different here (a device consuming data).
>
>
>
> Also thanks a ton for providing liblo as free software, it’s real helpful!
>
>
>
> Best,
>
> Roland
>
>
>
>
>
>
>
> *From:* Stephen Sinclair <rad...@gm...>
> *Sent:* Tuesday, August 4, 2020 6:16 PM
> *To:* liblo development list <lib...@li...>
> *Subject:* Re: [liblo] how to connect to a liblo TCP OSC server?
>
>
>
> Hi Roland,
>
>
>
>
>
> On Tue, Aug 4, 2020 at 1:36 PM Aigner Roland <
> rol...@fh...> wrote:
>
> However I struggle to figure out how I would connect a client to this
> server, i.e. what the code should look like for a client receiving the data
> sent by this server.
>
>
>
> I'm not sure if your concept of client and server is mixed up here?  In
> OSC it is the client sending data to the server.
>
>
>
> Documentation and sample code leave me scratching my head, I tried to
> figure out by checking the library source code, but so far I failed to
> understand. From the fact that lo_send_message_from requires a target
> address I infer that I would have to iterate through all connected clients
> and sent to the respective sockets manually.
>
>
>
> You can get a target address by creating one, if you know the destination,
> or you can get the sender's address from inside a message handler:
>
>
>
>     lo_address a = lo_message_get_source(data);
>
>     lo_send(a, "/hi", "i", 3);
>
>
>
> But how do I know when a client connection gets accepted?
>
>
>
> Who knows?  The server knows because a handler is being executed.  The
> client only knows whether the send failed.
>
>
>
>
>
> So, summarizing, my two remaining questions are
>
>    1. how do I connect a client to the server?
>
>
>
> Your code (which I snipped from the message, apologies) is correct.  You
> just create a server and specify LO_TCP for its protocol, and a client
> specifying LO_TCP for its protocol.  Then the client should be able to make
> a connection to the server and send it a message.
>
>
>
>
>
>
>
>    1. how do I know what clients are currently connected that I would
>    have to send my packages to?
>
>
>
> Hm, I don't think liblo provides a way to enumerate the current client
> connections.. could be interesting, but it's not too usual to want to
> broadcast to a random client.  Usually messages from the server are limited
> to _responses_ that are sent during message handlers, and in that case you
> can get the response destination using lo_message_get_source as I outlined
> above.
>
>
>
> Note that if your *client* wants to receive a response... actually it
> cannot, it needs to set up a *server* to receive the response, and use
> lo_send_from, specifying that server.  That's how the destination server
> can find where to send responses back to.  So for bidirectional messaging,
> each side has a server.
>
>
>
> If you need to broadcast a message to multiple servers, you can look into
> multicast or broadcast messaging, but that's for UDP.
>
>
>
> As for sending a message to all currently connected clients, I'm not
> sure.. I'll have to think on how to do that and whether it's a good idea.
> Theoretically it is possible.
>
>
>
> Keep in mind that OSC is typically a UDP protocol and is designed around
> one-way messaging.  Liblo incidentally supports responses, but it's common
> for UDP protocols to be unidirectional.
>
> On the TCP side, often clients will make a connection, send a message,
> *maybe* wait for a response, and then close the connection.  Long-lived
> connections are more rarely used; but if they are, they shouldn't *depend*
> on the connection state.
>
>
>
> Hope this helps,
>
> Steve
>
>
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