A TypeScript library that lets the different parts of a multiplayer GTA V server talk to each other as simply as calling a function. Open-source

In plain words

Every FiveM server is built from three parts:

the server, which holds the shared world and the rules
the game client on each player's computer
the in-game screens: menus, phones and shops, built as small web pages

These parts constantly need things from each other. For example, when a player presses "Buy" in a shop menu, the menu has to ask the server whether the player can afford the item and then show the answer

Out of the box, FiveM only lets these parts leave notes for each other. One side sends a message and never finds out whether anyone read it. Getting an answer back means wiring up a second message by hand every time, and it is easy to get wrong

FiveM RPC turns those notes into phone calls. One part asks and waits, and the other part answers. The call always ends in one of two ways: an answer, or a clear explanation of what went wrong

const bought = await rpc.emitServer('buyItem', 'water')

Why it matters

Nothing gets stuck. Every request ends within 5 seconds, with an answer or a readable error, so a menu never freezes waiting for a reply that will not come
Players cannot pretend to be someone else. The server gets each player's identity from the game itself, never from what the player's computer claims. A modified game client cannot act in another player's name or fake another player's answers
Mistakes are caught before the game even starts. Developers describe their messages once, and their code editor autocompletes names and flags typos and wrong data as they type
Errors explain themselves. Instead of "something failed", a developer reads, for example: No listener for "buyItem" on server. Register it with rpc.onClient("buyItem", ...) in server code
Friendly to AI coding assistants. The package ships a short guide that AI assistants can follow, so code they generate uses the library correctly

How it works

SERVER <-- network events --> CLIENT <-- NUI messages --> WEBVIEW

Where server - world and rules; client - player's game; webview - in-game menus. Calls between webview and server are relayed through the player's client

One entry point per part. createRPC({ env: 'server' | 'client' | 'webview' }) returns an object with matching pairs of methods: emit* to call, on* to answer
Ten call types, including calls within the same part and a server-wide broadcast to every player
Every call carries a unique id
- A pending call waits for the response with the same id, or times out
- On the server, a call only accepts a response from the player it was sent to
Listeners never crash the receiver. A missing or failing listener sends a structured error back, and the caller receives it as a typed RPCError
Typing is opt-in. With nothing declared, everything is accepted. Once a developer declares their events in a shared file, every call in all three parts is checked by the compiler

Inspired by altv-xrpc from the alt:V community

members

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