Hi all, I've been working on a sort of side-scrolling, shoot em up, RTS game for the past few weeks and am now confronting the issue of sending the game world to the client when it logs in. Right now, when the player logs in, the entire game world is sent all at once (each object gets it's own packet) over reliable UDP (I'm using enet). Originally, I had the game world all in one packet, but the packet was too big to send in just one packet (it's like 50kb). Right now, it works fine if you have fast internet, but with slow internet (50 kilobytes per second) the client will hang there for a very long time receiving only a few game objects a second and never really receives the entire game world.

Any suggestions? I'm about to implement a system where it spreads the packets out over a few seconds, is that a good fix? Or are there fancy ways that would be better?

Yes, it's a hot joinable game. Currently, each object get's it's own packet in the initial world send, and I mass send all of them at once.

Here is the relevant code:

void NetworkManager::send(sf::Packet &packet, int connectorID, int excludeID, bool reliable)
{
    sf::Packet finalPacket;
    //finalPacket << sf::Int8(0);
    finalPacket.append(packet.getData(), packet.getDataSize());

    // Create the enet packet
    unsigned int flags = 0;
    if (reliable)
        flags |= ENET_PACKET_FLAG_RELIABLE;

    ENetPacket *enetPacket = enet_packet_create(finalPacket.getData(), finalPacket.getDataSize(), flags);

    if (mType == NetworkType::CLIENT) // Clients send data to server only
    {
        enet_host_broadcast(mHost, 0, enetPacket);
    }
    else if (connectorID > 0) // It's a server and the client is specified. Tell only that client!
    {
        enet_peer_send(findConnector(connectorID)->mPeer, 0, enetPacket);
    }
    else // It's a server and the client is unspecified. Broadcast to everyone
    {
        if (excludeID > 0)
        {
            for (unsigned int i = 0; i < mConnectors.size(); i++)
            {
                if (mConnectors->mID != excludeID && mConnectors->mPeer)
                    enet_peer_send(mConnectors->mPeer, 0, enetPacket);
            }
        }
        else
            enet_host_broadcast(mHost, 0, enetPacket);
    }
}

void NetworkManager::sendSceneCreation(int connectorID, int excludeID, bool reliable)
{
    for (unsigned int i = 0; i < SceneManager::get()->getCurrentScene()->getGameObjects().size(); i++)
    {
        if (SceneManager::get()->getCurrentScene()->getGameObjects()->getSyncNetwork())
            sendGameObject(SceneManager::get()->getCurrentScene()->getGameObjects(), connectorID, excludeID, reliable);
    }
}

void NetworkManager::sendGameObject(GameObject *object, int connectorID, int excludeID, bool reliable)
{
    sf::Packet packet;
    packet << PacketType::CREATE_OBJECT;
    object->serialize(packet);

    send(packet, connectorID, excludeID, reliable);
}

Thanks for the suggestions, I'll cram stuff into bigger packets. Could you recommend a good maximum packet size? I'll make it adjustable and play with it, but I'd like a ball park This networking stuff is all very new to me.

And thanks, nfactorial, I've also given sending only immediate surroundings a thought, and that will be very easy since I already have stuff to detect which planet you are currently on (you fight across many 2D planets).

Edit: But also, in that regard, sending only the current surroundings is kind of the scenario at hand, since I only have 2 planets in the game right now. I plan on having around 100 planets in an actual match.