Roblox Networking

roblox-networking

When to Use

Use this skill when the task is primarily about multiplayer communication, replication, or trust boundaries in a Roblox experience:

• Designing or reviewing RemoteEvent, UnreliableRemoteEvent, and RemoteFunction usage.
• Deciding what the client is allowed to send versus what the server must derive or verify.
• Choosing safe remote payload shapes, validating arguments, and handling replication timing.
• Protecting server logic from spam, malformed payloads, impossible requests, or exploit-driven abuse.
• Building interactions where the client initiates an action but the server remains authoritative.
• Reasoning about network ownership, client-predicted physics, or Touched-related exploit risk.
• Applying server-authority ideas, prediction, rollback-aware structure, or input routing for competitive or authoritative gameplay.
• Designing multiplayer logic that must remain correct when streaming affects what the client can currently see or access.

Do not use this skill when the task is mainly about:

• Persistent data architecture, save formats, trading storage, or DataStore and MemoryStore design.
• Broad engine API lookup as the primary task.
• Open Cloud, OAuth, or external web integrations.

Decision Rules

• Use this skill if the main question is "how should client and server communicate safely and correctly?"
• Use this skill when a feature depends on remotes, replication timing, ownership of simulated parts, or server validation.
• Prefer RemoteEvent for one-way signals and state notifications; prefer UnreliableRemoteEvent only for disposable, continuously changing data; prefer RemoteFunction only when a synchronous reply is truly required.
• Treat the server as the authority for shared game state, rewards, combat outcomes, movement permission, and any action that affects other players.
• If a client can request an action, validate permission, context, type, structure, value range, and frequency on the server before mutating state or broadcasting results.
• If the task is mostly about where scripts live, core services, attributes, bindables, or basic runtime structure without a strong networking/security angle, hand off to roblox-core.
• If the task is mainly about data persistence or cross-server state, hand off to roblox-data.
• If the task is mainly about exhaustive class/member lookup, hand off to roblox-api.
• If a request mixes networking with out-of-scope systems, answer only the multiplayer and trust-boundary portion and explicitly exclude the rest.
• When unsure, omit material that would drift into persistence, cloud auth, or broad API catalog guidance.

Instructions

1. Start by classifying each piece of information:
   • Client input intent.
   • Server-derived authoritative state.
   • Replicated presentation or notification.
   • Disposable telemetry or cosmetic updates.
2. Choose the narrowest network primitive that matches the job:
   • RemoteEvent for async one-way communication.
   • UnreliableRemoteEvent for frequent data where dropped or out-of-order updates are acceptable.
   • RemoteFunction only for short, bounded request-response flows where yielding is acceptable and server ownership of the decision is clear.
3. Keep remote contracts explicit and small:
   • Prefer stable argument order and dictionaries with string keys.
   • Do not rely on metatables, function values, mixed tables, non-replicated instances, or table identity surviving a network hop.
   • Pass identifiers, compact values, or validated replicated instances instead of arbitrary object trees.
4. Design remotes around intent, not outcome:
   • Client says "I pressed interact on this target" or "I attempted to fire from here toward this hit point."
   • Server decides whether the action is legal and computes the result.
   • Avoid remotes where the client directly declares rewards, damage, inventory changes, or unrestricted instance mutations.
5. Validate every client-triggered request on the server:
   • Permission/context: is the player alive, in range, in the right state, and allowed to do this now?
   • Type/shape: are the arguments the expected kinds, sizes, and instance classes?
   • Value sanity: reject impossible numbers, NaN, inf, out-of-range vectors, or unknown ids.
   • Timing: apply per-player rate limits or cooldowns before expensive work or broadcast fan-out.
6. Treat server-to-client rebroadcasts as privileged operations:
   • Never act as a blind relay from one client to other clients.
   • Validate first, then broadcast only the minimal safe data needed for presentation.
7. Use RemoteFunction conservatively:
   • Expect the caller to yield.
   • Keep the callback fast and deterministic.
   • Avoid InvokeClient() for critical flows because the server can hang or fail if the client errors, disconnects, or never returns.
8. Reason about replication explicitly:
   • A remote arriving does not guarantee a related instance or property has already replicated to the client.
   • With streaming enabled, clients may not currently have distant workspace content.
   • Use WaitForChild(), replication-aware design, tags, or model streaming controls instead of assuming presence.
9. Treat network ownership as a performance tool with security cost:
   • Client-owned physics can feel responsive.
   • Client-owned physics can also be abused, and Touched-based server logic becomes especially risky.
   • Keep gameplay-critical physics server-owned unless the responsiveness tradeoff is worth the validation burden.
10. For authoritative or competitive gameplay:

• Prefer a server-authority mindset where the server is the source of truth and the client primarily contributes input.
• Use the Input Action System for inputs that affect the core authoritative simulation.
• Keep simulation state separate from local rendering and effects.

11. When discussing examples, stay inside scope:

• Focus on multiplayer communication, validation, ownership, authority, and streaming correctness.
• Do not expand into persistence architecture, cloud APIs, or general-purpose API catalogs.

Using References

• Open references/remote-events-and-callbacks.md for remote selection, directionality, argument-shape limits, and safe payload design.
• Open references/client-server-runtime.md for replication timing, latency expectations, and side ownership of gameplay responsibilities.
• Open references/security-and-defensive-design.md for the security mindset, defensive design, and rate-limiting patterns.
• Open references/client-server-boundary-guidance.md for concrete validation layers, secure rebroadcast patterns, and protection of client-triggered interactions.
• Open references/network-ownership.md when physics responsiveness, client-owned parts, or Touched validity are part of the problem.
• Open references/server-authority-model-and-techniques.md for authoritative simulation, prediction, rollback-aware structure, and latency-conscious design.
• Open references/input-action-system.md when networked or authoritative gameplay depends on action-oriented, cross-platform input routing.
• Open references/streaming-and-replication-behavior.md when correctness depends on streamed workspace content, replication focus, or models that may not be locally present.

Checklist

• The client-server contract is defined in terms of player intent, not client-declared outcomes.
• The chosen remote primitive matches the required reliability and response behavior.
• Remote payloads use stable, replication-safe shapes.
• The server validates permission, context, type, structure, and values before mutating shared state.
• The server applies rate limits or cooldowns to abuse-prone entry points.
• Server-to-client broadcasts happen only after validation and never as blind relays.
• RemoteFunction use is justified and bounded.
• Replication timing assumptions are explicit, especially when remotes reference freshly created or streamed content.
• Network ownership choices are deliberate and paired with server-side validation where needed.
• Touched, proximity, click, or drag interactions are not trusted just because the engine fired them.
• Authoritative gameplay uses client inputs and server-owned state rather than trusting client simulation results.
• Input guidance stays focused on networked or authoritative use of the Input Action System.
• No persistence architecture, Open Cloud, OAuth, or broad API catalog material is included.

Common Mistakes

• Letting the client tell the server who was damaged, what reward was earned, or which state change already happened.
• Using RemoteFunction for convenience when an async RemoteEvent plus server-side state would be safer.
• Broadcasting one client's payload to every other client without validating it first.
• Passing mixed tables, metatable-backed objects, huge payloads, or sender-only instances across remotes.
• Forgetting to reject NaN, inf, oversized strings, or spoofed instance references.
• Assuming a remote means an associated part, attribute, or model has already replicated.
• Relying on client cooldowns without server-side rate limiting.
• Treating client-owned physics or Touched events as authoritative proof of contact.
• Using unreliable channels for state that must arrive in order.
• Mixing core authoritative simulation logic with local-only animation, camera, or VFX code.

Examples

Design a secure client-triggered interaction

-- Client: request an interaction attempt, not the reward itself.
InteractRemote:FireServer(targetId)

-- Server: verify range, state, and target validity before applying effects.
InteractRemote.OnServerEvent:Connect(function(player, targetId)
    -- Validate player state, target existence, distance, cooldown, and permissions.
    -- Then mutate shared state on the server.
end)

Use unreliable remotes only for disposable updates

-- Suitable for frequent cosmetic aim or camera direction updates.
AimDirectionRemote:FireServer(lookVector)

• Accept dropped or out-of-order packets.
• Do not use this pattern for inventory, damage, scoring, or one-time transactions.

Keep authoritative simulation separate from rendering

-- Core state changes live in shared/server-side simulation logic.
-- Local VFX and sounds react to the synchronized state afterward.