Not translated yet — showing English.
Rooms
A room is a game session; the platform doesn't care what hosts it. One abstraction covers a dedicated server per match, one big shared map split into logical layers, a master-client-hosted room, and a backend-hosted mini-game. Room internals are ours; you drive a room from outside.
When to use it
- Your game has sessions (matches, lobbies, dungeons, races), and something must own their lifecycle, membership and reconnects.
- You host on dedicated servers, a player's master-client or the backend itself, and need players routed there.
- One shared map must run many logical sessions: layers, scoped by Visibility.
- Players join mid-session and must see the current state: the room's state on arrival, then live traffic.
- A dropped connection must not cost the seat: the template's grace window (45s in
battle) resumes the same membership. - Skip it when a feature is purely request/response over records. Plain Data already covers it.
Who does what
| Actor | On this page |
|---|---|
room-owner | registers rooms across the process; on one room instance — the per-instance admin interface: patches live config, kicks, locks, broadcasts, disposes |
entry-validator | accepts or rejects join requests with a code and a reason |
room-visitor | browses, joins with data, reconnects within grace window, leaves |
spectator | joins without contesting; receives broadcasts and live traffic |
match-organizer | reserves seats that count toward capacity; a reserve expires on the template's term (90s in battle) |
At a glance
battle template: capacity, tick, host kind, a named map, and the two seat windows[RoomTemplate("battle")]
public static class Battle
{
public static int Capacity = 8;
public static Tick Tick = Tick.Hz30;
public static Host Host = Host.Backend; // or DedicatedServer, MasterClient
public static MapRef Map = Maps.Named("arena-caves-v3");
public static Duration Grace = 45.Seconds(); // a dropped member keeps the seat this long
public static Duration Reserve = 90.Seconds(); // a reserved seat is held this long
}@RoomTemplate('battle')
export class Battle {
static capacity = 8;
static tick = Tick.hz30;
static host = Host.backend; // or Host.dedicatedServer, Host.masterClient
static map = Maps.named('arena-caves-v3');
static grace = seconds(45); // a dropped member keeps the seat this long
static reserve = seconds(90); // a reserved seat is held this long
}@room_template("battle")
class Battle:
capacity = 8
tick = Tick.HZ30
host = Host.BACKEND # or Host.DEDICATED_SERVER, Host.MASTER_CLIENT
map = maps.named("arena-caves-v3")
grace = seconds(45) # a dropped member keeps the seat this long
reserve = seconds(90) # a reserved seat is held this longAttribute-style declaration in Go is still open (O-1) — the samples land when the carrier is decided.
USTRUCT(PSRoomTemplate = (Name = "battle", Capacity = 8, Tick = 30,
Host = "Backend", // or "DedicatedServer", "MasterClient"
Map = "arena-caves-v3",
Grace = "45s", // a dropped member keeps the seat
Reserve = "90s")) // a reserved seat is held
struct FBattle { GENERATED_BODY() };
// declarations compile into the same pushed model — playserv push from the UE project or CI[RoomTemplate("battle")]
public static class Battle
{
public static int Capacity = 8;
public static Tick Tick = Tick.Hz30;
public static Host Host = Host.Backend; // or DedicatedServer, MasterClient
public static MapRef Map = Maps.Named("arena-caves-v3");
public static Duration Grace = 45.Seconds(); // a dropped member keeps the seat this long
public static Duration Reserve = 90.Seconds(); // a reserved seat is held this long
}Wherever it is authored, the pushed template is versioned and editable in the panel, so live-ops retunes a room type without an engine redeploy. Hosting rooms built from it is the same surface reached by a different role, and both an Unreal dedicated server and a master-client hold all of it — register, host several per process, patch live config, kick, publish, dispose.
entry-validator hook: banned players rejected at the door, with a code and a reason[Before(Rooms.Entry, room: "battle")] // the entry-validator interface
public static Verdict ValidateEntry(EntryRequest entry) =>
entry.Player.IsBanned
? Entry.Reject(Problem.Banned, "banned from this project")
: Entry.Accept();// the entry-validator interface
export const validateEntry = before(Rooms.entry, { room: 'battle' },
(entry: EntryRequest) =>
entry.player.isBanned
? Entry.reject(Problem.banned, 'banned from this project')
: Entry.accept());@before(rooms.entry, room="battle") # the entry-validator interface
def validate_entry(entry: EntryRequest) -> Verdict:
if entry.player.is_banned:
return entry.reject(Problem.BANNED, "banned from this project")
return entry.accept()Attribute-style declaration in Go is still open (O-1) — the samples land when the carrier is decided.
A hook is a cloud function: it executes on the platform, not in the engine. Write it in C#, TypeScript or Python — Unreal subscribes to the resulting events. Engine-authored functions are planned: Blueprint graphs, and C++ (translated to a platform-validated script target). Both are analyzed and pushed like any declaration; execution stays on the platform.
A hook is a cloud function: it executes on the platform, not in the engine. Write it in C#, TypeScript or Python — Unity subscribes to the resulting events.
Client:
var rooms = await playserv.Rooms.Browse("mode == 'ctf' && players < capacity");
var room = await playserv.Rooms.Join(rooms.First(), with: new { loadout = "scout" });
room.OnMemberJoined(m => Hud.Add(m));const rooms = await playserv.rooms.browse("mode == 'ctf' && players < capacity");
const room = await playserv.rooms.join(rooms[0], { with: { loadout: 'scout' } });
room.onMemberJoined((m) => hud.add(m));rooms = await playserv.rooms.browse("mode == 'ctf' && players < capacity")
room = await playserv.rooms.join(rooms[0], with_data={"loadout": "scout"})
room.on_member_joined(lambda m: hud.add(m))Attribute-style declaration in Go is still open (O-1) — the samples land when the carrier is decided.
Client->Rooms->Of<FBattle>()->Select()
.Where(PSFields::Room::Mode == TEXT("ctf"))
.Then(TPSOnResult<TPSPage<FPSRoomInfo>>::CreateWeakLambda(this, [this](const TPSResult<TPSPage<FPSRoomInfo>>& Found)
{
if (!Found.HasValue()) { return; }
// join the first match; the join data rides along
Client->Rooms->Join(Found.Value().Rows[0], FPSJoinData{{ TEXT("loadout"), TEXT("scout") }},
TPSOnResult<FPSRoom*>::CreateWeakLambda(this, [this](const TPSResult<FPSRoom*>& JoinResult)
{
if (!JoinResult.HasValue()) { return; }
TPSSubscription Roster = JoinResult.Value()->Subscribe->Presence(
[this](const FPSPresence& Presence) { Hud->Add(Presence); });
}));
}));
// co_await support ships later: a built-in SDK coroutine wrapper that respects Unreal's GC and threading.var rooms = await playserv.Rooms.Browse("mode == 'ctf' && players < capacity");
var room = await playserv.Rooms.Join(rooms.First(), with: new { loadout = "scout" });
room.OnMemberJoined(m => Hud.Add(m));The model
A room is a group with rules, and it is not an entity. Membership comes from groups; its system state is platform-level, while the game's state lives in entities scoped to it. And no consumer code runs inside a room — in either authority mode.
What a room type declares.
| Declares | What it is |
|---|---|
capacity | in seats, and a seat is the unit of capacity separated from membership: it may be reserved before a join and held through inactivity. A reservation is time-limited, with a declared deadline after which the seat is freed without a join |
visibility | enumerable · by name or code · hidden |
creation mode | one of three, and the on first join mode is obliged to declare an initialisation hook |
two independent timeouts | the idle timeout — how long a participant may be silent; and the empty-room TTL — how long a room with nobody in it survives |
rejoin window | within it a return restores the same membership and the same seat, rather than making a new participant |
authority mode | our simulation or external authority, and there is no default |
trust in a reported outcome | for external authority: accept it · check it with a hook · do not accept it. Again no default |
behaviour when the host drops | wait out the grace window · close the room · admit a replacement |
map instance and world strata | optionally, which instance it occupies and which strata inside it |
room-scoped entities | which of the studio's entities have the room's scope — expressed by a predicate, not by a new mechanism |
The two machines.
| Of | States |
|---|---|
| a room | created → open → closed → torn down, where torn down is terminal and closed means no new joins rather than gone |
| a membership | active ⇄ inactive → departed, with departed terminal for that membership |
What is true of every room.
| Always | What it is |
|---|---|
losing a connection and leaving | are different events, and the window's outcome is observable: "returned" and "the window expired" are distinguishable, so a client is never left guessing which happened |
a spectator | is not a degenerate participant: present, occupying no seat, and not in the roster addressed as "the players" |
no in-room roles | a room owner is an actor holding a right (Access), not a rank in the member list |
presence | has a history, the roster does not: who joined, dropped, returned and departed is kept; the roster's changes are not a second history |
the interface | is a specific room's: you address this room, not only its type |
three axes, not two | the API spanning every room (browse, register, list); the per-room API any member calls (join, leave); and a per-instance admin interface — kick, lock, patch config, close, dispose on this room — gated to whoever holds the admin or host role for that one instance rather than to membership |
The two authority modes.
| Mode | Who runs the tick |
|---|---|
| our simulation | our room implementation and its modules |
| external authority | a process running our SDK, in the room under an authoritative role: the studio's game server, or a player's client as the master-client |
What the mode decides, and what it does not.
| What it is | |
|---|---|
the line | is drawn by role, not by whose process it is. A dedicated server is the same client without the rendering; what separates it from a player's machine is trust, not construction — which is also why peer-to-peer needs no third mode, being a room in external-authority mode whose authority is a client host |
what is identical | entry rules, presence, reconnect and every declaration, across all three. What differs is only which process holds the authority and how much of it that process is granted |
the room does not move | no consumer code runs inside a room in either mode, and session and persistent state stay with us in both. A master-client is a member holding an authoritative role: the tick is computed there, the room does not live there |
Hosting a room.
var room = await playserv.Rooms.Register("battle", key: "caves-eu-1");
var second = await playserv.Rooms.Register("battle", key: "caves-eu-2"); // several per process
room.OnMemberJoined(m => Seat(m));
await room.SetConfig(c => c.Set("mapRotation", "night")); // live config, no restart
await room.Dispose();const room = await playserv.rooms.register('battle', { key: 'caves-eu-1' });
const second = await playserv.rooms.register('battle', { key: 'caves-eu-2' }); // several per process
room.onMemberJoined((m) => seat(m));
await room.setConfig((c) => c.set('mapRotation', 'night'));
await room.dispose();room = await playserv.rooms.register("battle", key="caves-eu-1")
second = await playserv.rooms.register("battle", key="caves-eu-2") # several per process
room.on_member_joined(lambda m: seat(m))
await room.set_config(lambda c: c.set("mapRotation", "night"))
await room.dispose()Attribute-style declaration in Go is still open (O-1) — the samples land when the carrier is decided.
Client->Rooms->Of<FBattle>()->Create(FPSIdempotencyKey(TEXT("caves-eu-1")),
TPSOnResult<FPSRoom*>::CreateWeakLambda(this, [this](const TPSResult<FPSRoom*>& Result)
{
if (!Result.HasValue()) { return; }
OnRoomUp(Result.Value());
}));
Client->Rooms->Of<FBattle>()->Create(FPSIdempotencyKey(TEXT("caves-eu-2")), OnSecondRoom);
// in OnRoomUp(FPSRoom* Room):
TPSSubscription Roster = Room->Subscribe->Presence([this](const FPSPresence& Presence) { Seat(Presence); });
Room->Config->Modify({ .MapRotation = TEXT("night") });
Room->Delete(); // demolish — the declared end of the room's existence
// co_await support ships later: a built-in SDK coroutine wrapper that respects Unreal's GC and threading.var room = await playserv.Rooms.Register("battle", key: "caves-eu-1");
var second = await playserv.Rooms.Register("battle", key: "caves-eu-2"); // several per process
room.OnMemberJoined(m => Seat(m));
await room.SetConfig(c => c.Set("mapRotation", "night")); // live config, no restart
await room.Dispose();| Always | What it is |
|---|---|
the handle | is the same object the client tab uses: there is no host bootstrap and no server-only handle. It answers these calls because the actor's role includes them at runtime — a dedicated server or a master-client running under a host key (Access) |
registration | takes an idempotency key, because a timeout on it is otherwise unrecoverable: repeat the call with the same key and you get the same room back, not a second one nobody knows the address of |
Entry, presence and reconnect.
| What it is | |
|---|---|
entry | is a validated request: the joiner supplies data at join and the entry hook accepts or rejects with a code and a reason. That data is what the member initialises itself from — in battle the loadout carried in at join is what the member's Tank spawns with |
seats and reservations | Matchmaking claims a seat for the template's reserve term — 90 seconds in battle — and the client then joins directly. Reservations count toward capacity, and expiry frees the seat with an event rather than silently |
a drop is not a leave | a disconnected member keeps their seat for the grace window (45s in battle) and reconnects into the same membership; expiry makes it a leave, and the event carries which of the two it was. Coming back one second late is told the room is alive and the membership is not — a different answer from "no such room" |
late join is state, not a journal | a joiner gets the room's current state and then live traffic |
Events aren't replayed after a reconnect
Events sent while a player was away are not replayed, for a late joiner or for a returning member. Anything that has to survive the gap must be state: the mine a player laid is a room-scoped entity, not a MinePlaced message somebody has to catch.
Errors
- A room that does not exist or is hidden by a predicate, and a torn-down room, answer not found — a refusal never reveals a room you may not see.
- Capacity exhausted is a conflict, and reserved seats count as occupied; worth repeating once a seat frees. Closed to joins is likewise a conflict, worth repeating if it opens.
- A join rejected by a rule is a conflict; rejected by a hook carries the hook's own code and reason, so "a rule of the game said no" never arrives looking like a transport failure.
- The rejoin window expired is a conflict: join as a new participant, with a new seat.
- A lapsed reservation is a conflict: take a new one.
- A map instance that is unavailable or does not exist is a validation refusal.
- A move the target room rejected is a conflict, and what to do depends on its reason.
- Creation beyond the room limit answers as a rate limit or a conflict depending on which limit it was.
Limits
The numbers arrive with the platform limits chapter; what happens at each ceiling is fixed now.
- A room's capacity: a join is refused as a conflict, with reserved seats counted as occupied.
- Rooms per project: creation is refused as a conflict.
- Rooms per actor: creation is refused, and rooms already created are never torn down to make space.
- The rate of room creation: a rate limit with a deadline.
- A participant's idle timeout: a forced departure with an event and a declared reason.
- The empty-room TTL: teardown with an event; switchable off on the persistent-zone type.
- A seat reservation's deadline: release with an event.
- Rooms on one map instance: creation on an occupied instance is refused unless the type declared shared occupancy.
- The size of a room event's payload: publication is refused before sending, never truncated.