Online multiplayer

import * as Net from "tts/net"

Real-time multiplayer for up to 6 players, plus a quick chat channel, built on Scratch cloud variables.

Me.ts

import * as Net from "tts/net";
import * as Input from "tts/input";

whenFlag(() => {
  Net.join();                                   // claims a free slot (takes ~2 s)
  forever(() => {
    me.x += Input.axisX() * 5;
    me.y += Input.axisY() * 5;
    Net.sendState(me.x, me.y, 0, 0);            // four numbers per player
    if (Input.pressedOnce("m")) Net.sendMessage(0); // "Hi!"
    const got = Net.pollMessage();
    if (got) say(Net.message);
  });
});

Others.ts

import * as Net from "tts/net";
let slot = 0;

whenFlag(() => {
  for (let i = 1; i <= Net.SLOTS; i++) { slot = i; createClone(); }
});

onClone(() => {
  forever(() => {
    const active = Net.readPlayer(slot);
    if (active && slot !== Net.session.slot) {
      me.visible = true;
      glide(0.1, Net.pa, Net.pb);               // smooth out the ~10 updates per second
    } else {
      me.visible = false;
    }
  });
});

The full demo is examples/multiplayer.

API

join()	watch the slots for 2 seconds, then claim a free one; sets session.slot (0 if full)
session.slot	this player's slot, 1–6, shared by all your sprites
sendState(a, b, c, d)	publish four whole numbers from -4999 to 4999 (position, direction, score...); throttled to 10 per second
readPlayer(slot)	read a player into pa, pb, pc, pd; true if they updated in the last 3 seconds
sendMessage(phrase)	send QUICK_CHAT[phrase] to everyone
QUICK_CHAT	the phrase list: Hi!, Good game!, Follow me!, Nice!, Oops!, Bye!
pollMessage()	true when someone else sent a new message; read message (the phrase) and messageFrom
SLOTS	6

Where it works

• scratch.mit.edu: the project must be shared, and players must be logged in with the Scratcher status (not "New Scratcher"). Scratch allows about 10 cloud updates per second per player; sendState stays under that.
• TurboWarp: works for everyone on the same project, with no account needed.
• In the editor, cloud variables behave like normal variables, so you can test the single-player parts.

How it works

The module declares 7 cloud variables (☁ p1–☁ p6 and ☁ msg). Scratch allows 10 per project, which leaves 3 for you. Each player writes only their own slot: a heartbeat plus four numbers, packed as digits. A player counts as active while their heartbeat keeps changing.

Why quick chat only

Scratch does not allow free-text chat in projects (it can not be moderated), so messages are a phrase number. You can change the phrases in QUICK_CHAT, but keep them to a fixed list.

Your own cloud variables

Mark an exported state object with @cloud:

/** @cloud */
export const highscores = { best: 0 };

Cloud variables hold numbers only, and each update is visible to every player of the shared project.