Networking

Question

You still sure you want to use networking in your game???

Networking in Isetta is completely messaging based, there are no Cmd or Rpc or SyncVars like in Unity. Our example networking level and NetworkTestComponent is the best place for you to get started.

A few things to definitely note:

• When implementing a network message class, you need to define both the Serialize and the Copy functions. Serialize MUST return true at the end of the function--otherwise your client will disconnect every time you try to send the message and you won't know why!
• Each of the serialization functions we use come from yojimbo, and they're the following:
  • serialize_int: Serializes an integer value and compresses that within the range of min and max
  • serialize_bits: Serializes the number of bits of a 32-bit value
  • serialize_bool: Serializes a boolean value using bits
  • serialize_float: Serializes a float value
  • serialize_uint32: Serializes a 32-bit unsigned integer value
  • serialize_uint64: Serializes a 64-bit unsigned integer value by serializing the low and high 32 bits
  • serialize_double: Serializes a double value by casting it to a 64-bit unsigned integer and serializing that
  • serialize_bytes: Serializes an array of bytes from a given pointer to data
  • serialize_string: Serializes a string of a given buffer_size
  • serialize_object: Serializes an object using a Serialize member function of the object that takes in the stream parameter

If you do use networking a lot, the team members in the room are probably the best documentation.

Essential API

• yojimbo::Message: The base class of the message objects
• NetworkManager::StartHost("hostIP")
• NetworkManager::StopHost()
• NetworkManager::StartServer("serverIP")
• NetworkManager::StopServer()
• NetworkManager::StartClient("clientIP")
• NetworkManager::StopClient()
• NetworkManager::SendMessageFromClient<MyMessage>(Action<MyMessage*> messageInitializer) where T inherits yojimbo::Message
• NetworkManager::RegisterClientCallback<MyMessage>(Action<yojimbo::Message*>)
• NetworkManager::SendMessageFromServer<MyMessage>(int clientIndex, Action<MyMessage*> messageInitializer)
• NetworkManager::RegisterServerCallback<MyMessage>(Action<int clientIndex, yojimbo::Message*>)
• NetworkManager::.SendMessageFromServerToAll<MyMessage>(MyMessage*)

Code Snippets

Defining a HandleMessage:

// HandleMessage simply sends an integer handle between 0 and 64 across the
// network
DEFINE_NETWORK_MESSAGE(HandleMessage)

// IMPORTANT: The Serialize function _must_ be a template around the Stream
// type, and it MUST return true at the end of the function. Otherwise the
// serialization will be assumed to have failed!
template <typename Stream>
bool Serialize(Stream* stream) {
  // serialize_int is supplied by yojimbo, along with many other primitive
  // type serialization functions
  serialize_int(stream, handle, 0, 64);
  return true;
}

// The Copy function must be overridden with boilerplate that copies the values
// from a given message. This is used for the general SendToAll functions that
// the NetworkManager has.
void Copy(const yojimbo::Message* otherMessage) override {
  const HandleMessage* message =
      reinterpret_cast<const HandleMessage*>(otherMessage);
  handle = message->handle;
}

public:
int handle = 0;  // Obviously we'll just use a handle

DEFINE_NETWORK_MESSAGE_END

Registering a callback for HandleMessage on the client:

exampleClientHandleId =
    NetworkManager::Instance().RegisterClientCallback<HandleMessage>(
        [](yojimbo::Message* message) {
          // We'll always have to cast our message into the message we're
          // anticipating
          HandleMessage* handleMessage = static_cast<HandleMessage*>(message);

          LOG(Debug::Channel::Networking, "Server sends handle #%d",
              handleMessage->handle);

          // Depending on the handle, we can do something (we tore out a
          // couple system here though)
          if (handleMessage->handle == 0) {
            LOG(Debug::Channel::Networking,
                "Server says we should play the animation!");
          }
          if (handleMessage->handle == 1) {
            LOG(Debug::Channel::Networking,
                "Server says we should stop the animation!");
          }
        });