Highly Performant & Scalable Ultima Online Server Emulator
https://www.modernuo.com
c-sharpcsharpcsharp-coredotnetdotnet-coreemulatorgplgplv3mmommo-enginemmorpgmmorpg-serveronlinerpgrunuoserverservuoultimaultima-onlineuo
967ddf48fa
## Problem
Contributing a ban to CrowdSec failed against a real LAPI — `POST /v1/alerts` answered **500**, and depending on the shard's locale, auth answered **401**. Three independent defects, each sufficient on its own.
## Fixes
**`scenario_hash` / `scenario_version` were never serialized.** LAPI dereferences both unconditionally when persisting an alert, so omitting them is a nil deref and a 500 rather than a validation error. Both are now emitted with the values a watcher without a hub scenario is expected to send (`""` and `"1.0"`).
**`start_at`/`stop_at` were formatted without an `IFormatProvider`.** `:` is the time separator *specifier* in a custom .NET format string, not a literal — a shard running under a culture like `fi-FI` emitted `T15.04.05.123Z`, which Go's `time.RFC3339` rejects, producing another 500. Non-Gregorian cultures (`th-TH`, `ar-SA`) would also shift the year. Formatting is now pinned to `InvariantCulture` in `FormatTimestamp`, which additionally converts non-UTC input — the trailing `Z` is a literal and was previously an unchecked claim.
**The `User-Agent` was a plain product string.** LAPI's default watcher profile matches the `crowdsec/` prefix and answers 401 without it, so the header is a protocol constraint, not cosmetic. It is now an `internal const` carrying that reason.
Also fixed, same root cause as the timestamp bug: the login-expiry parse used a bare `DateTime.TryParse` on LAPI's RFC3339 `expire`. Under a mismatched culture that silently fails and falls back to a fabricated `UtcNow + 1h`, pushing re-auth past the real expiry and costing a 401-relogin round trip on every send.
`capacity` now defaults to `1` instead of `0`, matching the one-decision-per-alert shape actually being sent.
## Note on scope
The two 500 causes are independent. On an `en-US` shard only the missing scenario fields were biting; the date bug was latent and would have surfaced as an unexplained regression the first time someone ran a shard under a European locale.
## Verification
The emitted payload is field-for-field identical to a hand-verified request that a live LAPI accepts:
```json
[
{
"scenario": "modernuo/rate-limit",
"scenario_hash": "",
"scenario_version": "1.0",
"message": "ModernUO rate-limit ban for 192.0.2.123",
"events_count": 1,
"start_at": "2026-07-27T15:04:05.123Z",
"stop_at": "2026-07-27T15:04:05.123Z",
"capacity": 1,
"leakspeed": "0s",
"simulated": false,
"events": [],
"remediation": true,
"source": { "scope": "Ip", "value": "192.0.2.123" },
"decisions": [
{
"origin": "modernuo",
"type": "ban",
"scope": "Ip",
"value": "192.0.2.123",
"duration": "300s",
"scenario": "modernuo/rate-limit"
}
]
}
]
```
Regression tests assert the required scenario fields on the **serialized JSON** rather than the DTO — the DTO is not what goes on the wire — and cover the timestamp as a `[Theory]` across `fi-FI`/`th-TH`/`ar-SA`.
`dotnet test --filter "FullyQualifiedName~CrowdSec"` → **21/21 passed**, build clean with 0 warnings.
|
||
|---|---|---|
| .config | ||
| .github | ||
| branding | ||
| dev-docs | ||
| Distribution/Data | ||
| Projects | ||
| tools | ||
| .cursorrules | ||
| .editorconfig | ||
| .gitattributes | ||
| .gitignore | ||
| AGENTS.md | ||
| azure-pipelines.yml | ||
| CLAUDE.md | ||
| CODE_OF_CONDUCT.md | ||
| CONTRIBUTING.md | ||
| Directory.Build.props | ||
| FAQ.md | ||
| GEMINI.md | ||
| global.json | ||
| LICENSE | ||
| ModernUO.slnx | ||
| publish.cmd | ||
| publish.ps1 | ||
| publish.sh | ||
| README.md | ||
| rider-settings.zip | ||
| Rules.ruleset | ||
| SPONSORS.md | ||
| stylecop.json | ||
| THIRD-PARTY-NOTICES | ||
| version.json | ||
ModernUO 
Ultima Online Server Emulator for the modern era!
Requirements
Supported Operating Systems
Required Frameworks
All Operating Systems
Windows
Development
Supported IDEs
Getting Started
- Install prerequisite requirements
- Clone this repository (or download the latest):
git clone https://github.com/modernuo/ModernUO.git
- Open
ModernUO.slnto start developing
Building/Publishing
Interactive Mode (Recommended for new users)
Run ./publish.cmd (Windows) or ./publish.sh (Linux/macOS) with no arguments to launch the guided build tool. It will:
- Check prerequisites (.NET SDK, native libraries)
- Walk you through configuration and platform selection
- Build and publish the server to the
Distributiondirectory - Show deployment instructions for cross-compiled builds
Command Line
./publish.cmd [release|debug] [os] [arch]
os- Supported operating systemsarchx64- Intel/AMD 64-bitarm64- ARM 64-bit
Linux Prerequisites
Fedora, CentOS, RHEL, AlmaLinux, Rocky, etc
dnf upgrade --refresh -y
# RHEL-family distributions (CentOS Stream, AlmaLinux, Rocky, RHEL) need CRB and EPEL enabled.
# Fedora skips this block.
dnf install -y dnf-plugins-core
dnf config-manager --set-enabled crb
dnf install -y epel-release
# Prerequisites
dnf install -y findutils libicu libdeflate-devel zstd libargon2-devel liburing-devel
Ubuntu, Debian, etc
apt-get update -y
apt-get install -y libicu-dev libdeflate-dev zstd libargon2-dev liburing-dev
OSX Requirements
brew install icu4c libdeflate zstd argon2
Running the Server
- Follow the publish instructions
- The
Distributiondirectory is portable — copy it to your production server for deployment - Run
ModernUO.exeordotnet ModernUO.dllfrom theDistributiondirectory - On first run, the server will prompt you to configure game data file locations
Troubleshooting / FAQ
- See FAQ
Want to sponsor?
Thank you for supporting us! You can find out how by visiting the sponsors page.
Collaborators
Thanks
- RunUO Team & Community
- Voxpire, the ServUO Team & Community
- Karasho, Jaedan and the ClassicUO Community
Development Tools & Plugins provided with ♥ by
Code Signing Policy
Free code signing provided by SignPath.io, certificate by SignPath Foundation.
This program will not transfer any information to other networked systems unless specifically requested by the user or the person installing or operating it
Teams & Roles
Approvers & Committers: Development Team