Empostor

Empostor is an open-source private server implementation for Among Us.

Features

• FriendCode support (authentication)
• Dynamic ports
• Admin Panel (dashboard)
• Plugin support
• Server-side anticheat

Getting Started

To run the server, you need:

• .NET 8.0 Runtime

Download the build you'd like from the releases. You most likely want the x64 build. Use the arm64 build if you are running Empostor on a Raspberry Pi, another ARM-based SBC, or an ARM VPS.

Unzip the file and go to config.json. To make your server playable for other devices, replace the "PublicIp" field with your actual public IP address.

It is also recommended to set up a Reverse Proxy (for HTTPS connections).

Client Setup

Windows

1. Go here and enter your server's IP/domain, port and name. Press "Download server file"
2. Press Win + R and enter this (leave the quotation marks):

"%userprofile%\AppData\LocalLow\Innersloth\Among Us"

3. Put the new regionInfo.json file you downloaded in the folder. Overwrite the existing file in the folder.
4. Launch Among Us. If everything worked, your server should appear in the regions list!

Android/iOS

1. Launch Among Us. When you reach the main menu, close the app.
2. Go here and enter your server's IP/domain, port and name.
3. Scroll until you see Instructions and press the Android or Apple logo.
4. Press "Open in Among Us". Among Us should open.
5. Your server should appear in the regions list!

Configuration

All settings live in config.json next to the server binary (a full sample is src/Empostor.Server/config.json). Unknown keys are ignored, so an old config keeps working after an update.

Section	Purpose
Server	Public IP/port, listen address and the dynamic (delta) UDP port range DeltaPortStart..DeltaPortEnd
HttpServer	Web API, admin panel and matchmaking token endpoint (Enabled, ListenIp, ListenPort)
AntiCheat	Server-side anticheat, including the IP request rate limit
Timeout	Spawn and connection timeouts
Compatibility	Game version compatibility rules
Debug	Game recorder
AuthApi	Friend code resolution (Mode: GameServices, Ume, Both or Off)
Admin	Admin panel password and marketplace URL
HPLP	HPLP public region listing

AntiCheat

Key	Default	Description
Enabled	true	Master switch of the anticheat
BanIpFromGame	true	Also block banned IPs on the game (UDP) side
AllowCheatingHosts	Never	What happens to hosts that cheat
EnableGameFlowChecks, EnableMustBeHostChecks, EnableOwnershipChecks, EnableRoleChecks, EnableTargetChecks	true	Game flow / state validation
EnableColorLimitChecks, EnableNameLimitChecks, EnableItemLimitChecks	true	Lobby limits (colors, names, items)
ForbidProtocolExtensions	true	Reject unknown/extension protocol messages
EnablePacketSizeChecks, PacketSizeLimit	true, 1203	Maximum inbound packet size
EnableIpRateLimit	true	IP request rate limit (below)
IpRateLimitRequests	30	Max TCP (HTTP) requests per IP per window, 0 disables the limit
IpRateLimitWindowMinutes	5	Length of the rate limit window in minutes

Ip request rate limit

Within one window (5 minutes by default) the same IP may only make IpRateLimitRequests (default 30) TCP (HTTP) requests — this protects the HTTP API against connection/request flooding. When the limit is exceeded:

• Every normal endpoint answers with 429 Too Many Requests and a localized hint, chosen from the request's Accept-Language header, e.g. 请求过于频繁请 5 分钟后重试. The Retry-After header says how many seconds are left.
• POST /api/user and PUT/GET /api/games (the whole join flow of the game client: matchmaking token + FindHost) are never rejected over HTTP — failing them there would only leave the client on a black screen, which just logs CoSendRequest failed and hangs. Both still count against the quota, and while an IP is over quota the server also skips the outbound friend code API calls (a cached/fallback code is used instead) so the endpoint cannot be abused for amplification. To keep a flooding IP from draining the dynamic port range, such joins are not given a pool port: they all receive the same shared reject port, a single pre-bound UDP socket whose only job is to answer the handshake with the localized hint in the client's own language (请求过于频繁请 5 分钟后重试) and close it again — the player is told why they cannot join instead of seeing a black screen, and only one socket is used no matter how many requests arrive. GamesController echoes the token's port back, so the client is naturally sent to that reject port. In fixed-port mode (DeltaPortStart=0) the main port is used instead.
• /admin and /api/admin are neither counted nor limited, so the dashboard can never lock the operator out.

The message lives under the key ratelimit.too_frequent in Languages/*.json (and in the built-in defaults in LanguageService.cs), so you can reword or translate it there. Set IpRateLimitRequests to 0 to turn the whole feature off.

Empostor usually runs behind a CDN or reverse proxy, so the real client IP is taken from the X-Real-IP header, then from the first entry of X-Forwarded-For, and only afterwards from the socket address. Make sure your CDN/proxy forwards one of these headers — otherwise every player would share the proxy IP's quota. Note that the game client polls some endpoints (e.g. /api/games) while you play: if 30 per 5 minutes is too tight for your players, raise IpRateLimitRequests (for example to 120).

Contributing

Please read the contributing guidelines.

You're welcome to open a pull request/issue!

Documentation

The documentation is available here!

License

This project is licensed under the GPL-v3.0 License.

Credits

• Impostor
• Next-Impostor
• NextFast.Hazel
• Reactor.Impostor