Multiplayer Messages

Messages represent one-time actions that do not need to be stored and interpolated as state.

Method List

Actions:

• gp.multiplayer.sendMessage() - send a one-time event to other players. FREE

Events:

• gp.multiplayer.onMessage() - subscribe to multiplayer messages. FREE
• gp.multiplayer.offMessage() - unsubscribe from multiplayer messages. FREE

Use messages for events such as:

• a player firing a weapon;
• an explosion or visual effect;
• an emote;
• starting or restarting a round;
• interaction with a map object.

Use player state or global state when late snapshots must still contain the value.

Receive Messages

Register one handler and route messages by eventName:

JavaScript

function onMultiplayerMessage({
    eventName,
    senderId,
    data,
    timestamp,
}) {
    if (eventName === 'shoot') {
        createBullet({
            ownerId: senderId,
            x: data.x,
            y: data.y,
            direction: data.direction,
        });
    }

    if (eventName === 'emote') {
        showEmote(senderId, data.name);
    }
}

gp.multiplayer.onMessage(onMultiplayerMessage);

Unity

void OnMultiplayerMessage(GP_Data message)
{
    Debug.Log(message.Data);
}

GP_Multiplayer.onMessage(OnMultiplayerMessage);

The handler receives:

Field	Description
eventName	Message type defined by the game
senderId	ID of the player who sent the message
data	Arbitrary JSON-compatible payload
timestamp	Message creation time

Send to Other Players

With no target, the message is sent to all other players:

JavaScript

gp.multiplayer.sendMessage('shoot', {
    x: player.x,
    y: player.y,
    direction: player.direction,
});

Unity

GP_Multiplayer.sendMessage(
    "shoot",
    new GP_Data(@"{
        ""x"": 100,
        ""y"": 200,
        ""direction"": 1
    }")
);

'all' can be passed explicitly:

JavaScript

gp.multiplayer.sendMessage(
    'roundStarted',
    { round: 2 },
    'all',
);

Unity

GP_Multiplayer.sendMessage(
    "roundStarted",
    new GP_Data(@"{ ""round"": 2 }"),
    "all"
);

To send a message to one player, pass their playerId:

JavaScript

gp.multiplayer.sendMessage(
    'privateEmote',
    { name: 'wave' },
    targetPlayerId,
);

Unity

GP_Multiplayer.sendMessage(
    "privateEmote",
    new GP_Data(@"{ ""name"": ""wave"" }"),
    targetPlayerId
);

Process a Message Locally with Echo

By default, the sender does not receive their own message. Use echo: true to run the same local handler immediately:

JavaScript

gp.multiplayer.sendMessage(
    'explosion',
    {
        x: 320,
        y: 180,
        radius: 80,
    },
    {
        target: 'all',
        echo: true,
    },
);

Unity

GP_Multiplayer.sendMessage(
    "explosion",
    new GP_Data(@"{
        ""x"": 320,
        ""y"": 180,
        ""radius"": 80
    }"),
    new MultiplayerSendMessageOptions
    {
        target = "all",
        echo = true
    }
);

The sender receives the echoed event locally without waiting for a network round trip. Other players receive it through multiplayer normally.

This is useful when all clients, including the sender, should execute the same event handler.

Choose an Authority Model

Messages transport an event but do not validate game rules. Decide which client is allowed to produce or confirm an event.

For host-authoritative actions, peers can send a request and the host can broadcast the accepted result:

JavaScript

function onMultiplayerMessage({ eventName, senderId, data }) {
    if (eventName === 'requestOpenChest' && gp.multiplayer.isHost) {
        if (canOpenChest(senderId, data.chestId)) {
            openChestInGlobalState(data.chestId);

            gp.multiplayer.sendMessage('chestOpened', {
                chestId: data.chestId,
                playerId: senderId,
            });
        }
    }
}

gp.multiplayer.sendMessage('requestOpenChest', {
    chestId: 'chest-7',
});

Unity

void RequestOpenChest(string chestId)
{
    GP_Multiplayer.sendMessage(
        "requestOpenChest",
        new GP_Data($@"{{ ""chestId"": ""{chestId}"" }}")
    );
}

// On the host, validate the message received through onMessage(),
// update globalState, and send the accepted result to all players.

The durable result belongs in globalState; the messages represent the request and notification.

Unsubscribe

Pass the same function reference used during subscription:

JavaScript

gp.multiplayer.offMessage(onMultiplayerMessage);

Unity

GP_Multiplayer.offMessage(OnMultiplayerMessage);

Stay in Touch

Other documents of this chapter are available here. To get started with GamePush, see the Tutorials chapter.

GamePush Community Telegram: @gs_community.

For your suggestions e-mail: official@gamepush.com

We Wish you Success!