Duck Game: Netcode guide for modders

Understanding that, how the netcode works will make your weapons / items compatible with multiplayer without having to do a bunch of tests, and if you don't have friends or two computers, it can save hours of unnecessary debugging and hopeless situations.
P.s this guide is a translation. Original: https://steamcommunity.com/sharedfiles/filedetails/?id=1394086869

public StateBinding _frameBinding = new StateBinding("spriteFrame", -1, false, false);
public byte spriteFrame {
      get {
        if (this._chargeAnim == null)
          return (byte) 0;
        return (byte) this._chargeAnim._frame;
      }

      set {
        if (this._chargeAnim == null)
          return;
        this._chargeAnim._frame = (int) value;
      }
    }

public StateBinding _netBounceSoundBinding = (StateBinding) new NetSoundBinding("_bounceSound "); //Statebinding для _bounceSound
public StateBinding _netYellSoundBinding = (StateBinding) new NetSoundBinding("_netYellSound "); //StateBinding для _netYellSound

public NetSoundEffect _bounceSound = new NetSoundEffect(); //Пустой SoundEffect, который будет привязан к функции.

public NetSoundEffect _netYellSound = new NetSoundEffect(new string[3]
    {
      "quackYell01",
      "quackYell02",
      "quackYell03"
    }); //Создание нового NetSoundEffect, который, будучи единожды воспроизведён, запустит три новых звука, и его синхронизация, чтобы остальные игроки услышали новый звук.
public override void Initialize()
{
    _bounceSound.function = new NetSoundEffect.Function(Bounce);
}

void Bounce()
{
    SFX.Play(GetPath("myBounceSound.wav"));
    shake = 5f;
}

public StateBinding _laserStateBinding = (StateBinding) new StateFlagBinding(new string[3]
{
"_charging",
"_fired",
"doBlast"
});
public bool doBlast;
public bool _fired;
public bool _charging;

Example taken from HugeLaser. Actually, fields _charging and_fired are not used in it, and it depends on the sprite frame and animation index, which, in turn, synchronized. And this is the best way to call, otherwise there would be a delay between all clients. Moreover, in Writing Proper Code this works with StateBindigs (parts).

Types of StateBindigs, which you don't need to know, since they are only used for optimization:

DataBinding(string field) – Works more efficiently with BitBuffers, and only with them.
CompressedVec2Binding – Reduces Vec2 size. All constructors come with maximum values.
CompressedFloatBinding – Decreases float size. All constructors come with maximum values.
InterpolatedVec2Binding[/b] – Highest priority CompressedFloatBinding extension.

[h]How to write correct code, which works with StateBindinds.[/h]
This is especially important if you’re dealing with stuff like timers or values that change rapidly. Basically what you have to do is write your stuff as if they could randomly skip a bunch of numbers and still work in the end.

This is especially important, if you are dealing with timers or values, which change rapidly. Essentially you need to write the code like this, as if it can accidentally skip a few numbers and still work

Here's an example: You have a float timer, which decreases its value every frame, and as soon as it reaches zero, something is happening.
Here, how to do not worth it:

timer–;
if(timer == 0) doStuff();

This works great in local play; but online, each frame can only send a limited amount of data, and most likely the timer value will decrease every three or more frames. In this case, the timer will decrease like this(assuming, what does it start with 10):
10 -> 10 -> 10 -> 7 -> 7 -> 5 -> 5 -> 5 -> 2 -> 2 -> 2 -> -1 -> -1 -> -3……
How do you see, 0 was skipped and doStuff() never started.

Here, How to fix it:

timer–;
if(timer <= 0) doStuff();

Easily, is not it? And it will really work!
It was because of this that there was a bug with an endless loading of the Internet map. London (developer) used ==, and when the required number was skipped due to the curves of the maps, it went further into infinity. Fortunately, it was fixed in beta.

Although, this is only half of the puzzle, as it is equally important to choose the correct values ​​for synchronization. In addition to the _charging and_fired fields, Huge laser – this is a great example of, what timers should look like.

Briefly, then here, what is happening there: 2 StateBinding for animations, using animation index and sprite frame. This can be used to synchronize animations.

StateFlagBinding is very useful, when you are dealing with multiple booleans, eg, if something is open, closed or blocked.

It's just a faster way to do multiple logical state bindings, which is actually pretty much outdated.

Parameters must be bool to use, and then their values ​​will be compressed into one ushort. Using ushort means, that you can't have more 16 logical fields.

public StateBinding _laserStateBinding = (StateBinding) new StateFlagBinding(new string[3]
{
"_charging",
"_fired",
"doBlast"
});
public bool doBlast;
public bool _fired;
public bool _charging;

Example taken from HugeLaser. Actually, fields _charging and_fired are not used in it, and it depends on the sprite frame and animation index, which, in turn, synchronized. And this is the best way to call, otherwise there would be a delay between all clients. Moreover, in Writing Proper Code this works with StateBindigs (parts).

Types of StateBindigs, which you don't need to know, since they are only used for optimization:

DataBinding(string field) – Works more efficiently with BitBuffers, and only with them.
CompressedVec2Binding – Reduces Vec2 size. All constructors come with maximum values.
CompressedFloatBinding – Decreases float size. All constructors come with maximum values.
InterpolatedVec2Binding[/b] – Highest priority CompressedFloatBinding extension.

[h]How to write correct code, which works with StateBindinds.[/h]
This is especially important if you’re dealing with stuff like timers or values that change rapidly. Basically what you have to do is write your stuff as if they could randomly skip a bunch of numbers and still work in the end.

This is especially important, if you are dealing with timers or values, which change rapidly. Essentially you need to write the code like this, as if it can accidentally skip a few numbers and still work

Here's an example: You have a float timer, which decreases its value every frame, and as soon as it reaches zero, something is happening.
Here, how to do not worth it:

timer–;
if(timer == 0) doStuff();

This works great in local play; but online, each frame can only send a limited amount of data, and most likely the timer value will decrease every three or more frames. In this case, the timer will decrease like this(assuming, what does it start with 10):
10 -> 10 -> 10 -> 7 -> 7 -> 5 -> 5 -> 5 -> 2 -> 2 -> 2 -> -1 -> -1 -> -3……
How do you see, 0 was skipped and doStuff() never started.

Here, How to fix it:

timer–;
if(timer <= 0) doStuff();

if(isServerForObject)
  Level.Add(new Crate(500,500));

Yes, you need an additional condition, and that's why:

Since each client has their own weapon code running, заспавнится 2 boxes; one locally, and the second from the owner of the object.
isServerForObject checks, whether the current computer owns the object, so that the object spawns only once.

Actually, you can check, is the duck local, using isServerForObject.

Actually, there is one more thing, which you should know about, and this is Fondleing. In fact, it allows you to take control of the thing and establish a connection.

public void Fondle(Thing t)
    {
      if (t == null || !Network.isActive || (!this.isServerForObject || !t.CanBeControlled()) || (this.connection != DuckNetwork.localConnection || t.connection == this.connection))
        return;
      t.connection = this.connection;
      ++t.authority;
}

public static void UpdateNetmessageTypes()
public static void UpdateNetmessageTypes() {
IEnumerable subclasses = Editor.GetSubclasses(typeof(NetMessage));
    Network.typeToMessageID.Clear();
    ushort key = 1;
    foreach (System.Type type in subclasses)
    {
        if (type.GetCustomAttributes(typeof(FixedNetworkID), false).Length != 0) {
            FixedNetworkID customAttribute = (FixedNetworkID)type.GetCustomAttributes(typeof(FixedNetworkID), false)[0];
            if (customAttribute != null)
                Network.typeToMessageID.Add(type, customAttribute.FixedID);
        }
    }
    foreach (System.Type type in subclasses) {
        if (!Network.typeToMessageID.ContainsValue(type)) {
            while (Network.typeToMessageID.ContainsKey(key))
                ++key;
            Network.typeToMessageID.Add(type, key);
            ++key;
        }
    }
}

public override void OnPostInitialize() {
    UpdateNetmessageTypes();
}

public override void OnPostInitialize() {
    UpdateNetmessageTypes();
}

Voila, now you can use NetMessage in your mod.

In fact, all NetMessage, which you will use, these are events (events).
You can also use regular NetMessage(NMDuckNetwork), but only if you send data to others, such as custom hats.

Your hypothetical NetMessage works something like this:
OnSerilize override fills the serializedData bitbuffer with data from every field in your class (as opposed to StateBidning, properties don't work), then they are forwarded by interveb(interwebs), where upon receipt they go through OnDeserilize override, where it puts all the values ​​from the bitbuffer into the correct fields.

For all Netmessages you need one empty constructor, because, when you get the message, a new object of this type will be created, using an empty constructor. If you don't have it, you will be crushed (not an anime player).

Here, what a simple NetMessage looks like:

class NMTimeLimit : NMDuckNetworkEvent
    {
        public string message;
        public NMTimeLimit()
        {

        }

        public NMTimeLimit(string msg)
        {
            message = msg;
        }

        public override void Activate()
        {          
            base.Activate();
            HUD.AddInputChangeDisplay(message);
        }

    }

Here is a list of all data types, which will be automatically serialized and deserialized(very important, to make the fields public! otherwise they will not be serialized):

• string
• float
• double
• byte
• sbyte
• bool
• short
• ushort
• int
• uint
• long
• ulong
• char
• Vec2
• Everything, what inherits or is Thing

When applying this to ducks: use byte for netIndex.

duck.profile.networkIndex

and then find a duck, using

DuckNetwork.profiles[(int) index].duck;

In this way, all your messages, duck related, will ship much faster, and the chances of out of sync will be greatly reduced.

And what, if you want some kind of array? Since it is not automatically supported, we will have to change the OnSerilize and OnDeserilize overrirides.

int[] myArray = new int[] { 25,30,29};
protected override void OnSerialize()
{
      base.OnSerialize(); //это то, что автоматически сериализирует поля, так что не убирайте это.

      serializedData.Write(myArray.Length);
      foreach (var num in myArray)
             serializedData.Write(num); //то же самое, что и в примере с BitBuffer'ом

public override void OnDeserialize(BitBuffer msg)
{
      base.OnDeserialize(msg); //автоматически десериализирует поля, не убирайте это.
      //так как при сериализации base.OnSerilize выполнялся первым, base.OnDeserilize тоже должен выполняться первым.

      myArray = new int[msg.ReadInt()];
      for (int i = 0; i < myArray.Length; i++)
          myArray[] = msg.ReadInt();
}
//по сути, вам нужно выяснить, как превратить что-либо в BitBuffer