[ENet-discuss] how to know when it's safe to call enet_peer_send()?

[Lee Salzman]

Use something like:

  if (peer -> reliableDataInTransit + size_of_packet_you_wish_to_send + 
100 < peer -> windowSize)
     ...

where that "100" value is just a margin/fudge value to account for 
packet headers and such.

Lee

eye at dihalt.com wrote:
> Hello.
>
> I'm new to enet and in the process of testing it right now.
> I'm interested is it possible to send huge amounts of data
> (audio, video etc) using enet. For now i have a few
> questions and will be happy is someone experienced with
> ENET will write me a few words of wisdom.
>
> 1. Let's assume that we have a fast network (100 megabit+)
> and a fast computer (3Ghz+). How to call enet_peer_send()
> so it will not eat all memory? Following example of
> "unlimited speed test" just eats up all memory becouse data
> is supplied to enet faster than enet can send it over
> network:
>
> for(; ::enet_host_service(poHost, &oEvent, 0) >= 0);)
> { // timeout '0' is used to achiev speed > 1k packets / sec
>   ENetPacket *poPacket = ::enet_packet_create(pbData, 1024,
>     ENET_PACKET_FLAG_RELIABLE);
>   _ASSERT(poPacket);
>   _VERIFY(0 == ::enet_peer_send(poPeer, 0, poPacket));
> }
>
> So i need to somehow make pauses between enet_peer_send()
> calls to give enet
> a chance to send previously queued data over network. Ok,
> following code will do a deal:
>
> for(; ::enet_host_service(poHost, &oEvent, 0) >= 0);)
> {
>   // do some magic: if > 64k of data is sent but is not
> ACK'ed yet - don't
>   // send new data to prevent overflow
>   if(poPeer->reliableDataInTransit > 1024*64) continue;
>
>   ENetPacket *poPacket = ::enet_packet_create(pbData, 1024,
>     ENET_PACKET_FLAG_RELIABLE);
>   _ASSERT(poPacket);
>   _VERIFY(0 == ::enet_peer_send(poPeer, 0, poPacket));
> }
>
> But if this method is correct, it leads to a second
> question:
>
> 2. What is the best method to determine if it's ok to make
> a enet_peer_send() call or not? For example, previous
> example uses hard-coded limit equal to 64kb of unacked data
> in transit. But such limit will result in unacked packets
> (and disconnection) on slow GPRS connection where speed is
> 4-10 kb/sec and 1000ms is a common png value. Vise versa,
> on 100 megabit network this 64k limit will slow down a
> process since network can handle much more data in transit.
>
> So, i'm confused a bit about how to send huge amounts of
> data with good speed on good connections AND no disconnects
> on bad connections. Any ideas? My current code analyses
> network speed and maintains ~ 1 seconds of data to be in
> transit. But this slows down transfer on fast connection,
> and on artifical 14kbit simulated network huge enough
> packets (like 16kb per packet) still gives disconnects :(.
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