Highly Performant & Scalable Ultima Online Server Emulator
https://www.modernuo.com
c-sharpcsharpcsharp-coredotnetdotnet-coreemulatorgplgplv3mmommo-enginemmorpgmmorpg-serveronlinerpgrunuoserverservuoultimaultima-onlineuo
23dc6649a0
## Why ModernUO mandated `-dev` packages on production servers for exactly one reason: `DllImport` never asks for a versioned SONAME, so `libdeflate.so.0` and `libargon2.so.1` sitting in `/usr/lib` went unfound, and the `-dev` package's unversioned symlink was the only thing making resolution work. The `-dev` packages ship no library of their own — operators were installing headers and a static lib on machines that compile nothing. Fixed in the binding packages (modernuo/LibDeflate.Bindings#4, modernuo/Argon2.Bindings#13), so this picks them up and stops asking. ``` LibDeflate.Bindings 1.0.3 -> 1.0.4 Argon2.Bindings 1.17.0 -> 1.19.0 ``` ## zstd is dropped too, on every platform ZstdNet bundles `libzstd` for `linux-x64`, `linux-arm64`, `osx-x64`, `osx-arm64` and win, and nothing shells out to the CLI. Verified: the 15 `ManagedArchive` round-trip tests pass in a container with no `zstd` package installed and `which zstd` empty. Removed from the README, the macOS `brew install`, and CI — so the macOS runners now prove it rather than us assuming it. ## NativeLibraryChecker asks a different question It asked *"is package X installed"* via `dpkg -l` / `rpm -q`. That is what forced `-dev`, and no hardcoded name works for ICU anyway — its apt package is release-specific (`libicu70` on Ubuntu 22.04, `libicu76` on Debian 13). It now asks *"will the loader find this"*: `NativeLibrary.TryLoad` on the unversioned name, then `libfoo.so.N` descending through the range the runtime accepts. It deliberately does not consult a package database or `ldconfig -p`. Both answer a different question than "will `dlopen` succeed" — see the ICU section below for how that bit. ## What was wrong with the ICU check `libicuuc` was **inherited, not derived**. It came from translating the old package-name check into a library probe, without establishing which library that should be. Reviewing it turned up three defects, all of which could report ICU present on a host where the runtime then refuses to start: - **`libicui18n` was never probed.** The only ICU names in `libSystem.Globalization.Native.so` are `libicuuc` and `libicui18n`. `libicudata` arrives as a dependency of `libicuuc`, and `libicuio`/`libicutu`/`libicutest` are never referenced — so that is the complete list, and both are checked now. - **No version floor.** The runtime's `MinICUVersion` is 60, but the probe accepted down to `.so.0`. RHEL/CentOS 7 ships ICU 50, which passed and then aborted at startup. - **The `ldconfig` fast path bypassed the range.** A cache line for `libicuuc.so.50` still matches a `libicuuc.so` prefix test, so the floor was unenforceable through it. It also trusts a stale cache — observed reporting a deleted `libdeflate` as present. Removed in favour of asking the loader directly, which reads the same cache but answers the real question, and which also deletes the musl special-case (`ldconfig -p` exits 0 on musl while producing nothing usable). Worth knowing when this goes wrong in the field: **missing ICU does not throw, it `FailFast`s** — SIGABRT, exit 134, uncatchable. The process starts cleanly and dies later at whatever line first touches a culture, so the stack rarely implicates ICU. ## tzdata is a separate prerequisite, and nothing was checking it The event scheduler resolves configured zone IDs through `TimeZoneInfo`, which reads `/usr/share/zoneinfo`. It is data rather than a library, so no loader probe finds it, and slim container images routinely omit it. Without it every lookup except `UTC` throws `TimeZoneNotFoundException` and `GetSystemTimeZones()` returns 1 entry instead of ~419. There is no per-zone packaging to opt into — it is ~2 MB for the whole set. The one split that does exist is a trap rather than an optimization: Debian 12 and Ubuntu 24.04 move the legacy aliases into `tzdata-legacy`, so plain `tzdata` has `America/New_York` and `EST5EDT` but is **missing `US/Eastern` and `Asia/Calcutta`**. A shard configured with a legacy alias throws even though tzdata is installed. Documented, with both fixes. ## Why `InvariantGlobalization` stays false Dropping ICU entirely by turning on invariant mode looks tempting and is not safe. Because `Directory.Build.props` also sets `PredefinedCulturesOnly=false`, invariant mode does **not** throw `CultureNotFoundException` — it silently hands back invariant data. Measured on .NET 10: | Behaviour | With ICU | Invariant mode | |---|---|---| | `new CultureInfo("de-DE")` | real culture | succeeds, returns invariant data | | de-DE decimal separator | `,` | `.` | | `1234.5` as de-DE | `1.234,5` | `1,234.5` | | `string.Compare("a", "B", InvariantCulture)` | `-1` (linguistic) | `31` (ordinal) | | sort `[b, A, a, B]` | `a, A, b, B` | `A, B, a, b` | | `FindSystemTimeZoneById("Eastern Standard Time")` on Linux | resolves | `TimeZoneNotFoundException` | | UTF-8 round-trip of non-ASCII | unaffected | unaffected | Number parsing and formatting produce wrong values with no error, and culture-sensitive sort order silently becomes ordinal. Encoding is not the mechanism — UTF-8 round-trips fine either way. ## Documentation The rationale now lives in `dev-docs/platform-prerequisites.md` rather than in comments, so it is discoverable without reading the build tool: what each dependency is for, what breaks without it, per-distro package names, the ICU floor, the `tzdata-legacy` split, and why the check asks the loader instead of the package manager. README drops `libicu-dev`. Matching the runtime package by pattern (`'^libicu[0-9]+$'`) is version-independent without pulling in headers, so **no `-dev` package is required on any supported distribution** — which was the point of the whole change. ## CI now proves the claim instead of contradicting it The dnf job already installed runtime packages only. The apt job installed `libicu-dev`, which ships the unversioned `libicuuc.so` symlink — so every probe succeeded on the first attempt and the versioned-SONAME fallback this PR depends on was never exercised. Switched to the pattern match, verified to resolve exactly one package on jammy (70), bookworm (72), noble (74) and trixie (76). Added an assertion that the unversioned symlinks are absent. Without it the suite silently stops testing anything the moment a base image starts shipping one. Verified against all eight matrix distributions — none ship them — and confirmed the step fails as intended when a symlink is planted. ## Audit of every other native entry point Checked whether anything else has the same hazard. It does not: | Import | Verdict | |---|---| | `ws2_32.dll` — `SocketHelper` | Always present on Windows | | `libc` — `SocketHelper` | **Verified safe**, see below | | ZstdNet → `libzstd` | Bundled for every RID | | IORingGroup | No native library; raw syscalls | | ICU | Loaded by the .NET runtime itself, which probes versioned suffixes | `libc` deserved a hard look, because `libc.so` *is* a `libc6-dev` linker script while the real library is `libc.so.6` — the same shape as the bug being fixed. It is not affected. Measured in a container with no `libc6-dev`: ``` /usr/lib/x86_64-linux-gnu/libc.so ABSENT /lib/x86_64-linux-gnu/libc.so.6 present TryLoad("libc") LOADED <- resolves where "libdeflate" would not TryLoad("libc.so") not found getpid() -> DllImport("libc") WORKS ``` Confirmed on Alpine/musl as well. No code in this repo registers a `DllImportResolver`, and nothing else P/Invokes. ## `--check-prereqs` New flag. `Program.cs` only ran the SDK check in non-interactive mode — `NativeLibraryChecker` was reachable only through the Spectre-driven guided flow, so there was no way to verify a deployment target from a script or a container. It is what made the container verification below possible, and it prints the exact ICU package for the running release via `apt-cache`. It renders through the same `PrerequisiteChecker` the guided menu uses, rather than a second hand-rolled table that could drift from it. Spectre drops ANSI styling on its own when stdout is not a terminal, so redirected output stays clean; the console width is widened in that case so the install hints, which are shell commands meant to be copied, do not gain a newline mid-command. ``` ╭───────────────────────────╮ │ Checking native libraries │ ╰───────────────────────────╯ ✔ libicuuc (Found) ✔ libicui18n (Found) ❌ libdeflate (Not found) ❌ tzdata (Not found — every zone except UTC will throw) ⚠️ Install the missing dependencies. The -dev/-devel packages are not required: sudo apt-get install -y libicu74 libdeflate0 tzdata ``` Exit code carries the machine-readable half: 0 when everything resolves, 1 when anything is missing. ## Verification Against 1.0.4 and 1.19.0: build plus **810 Server.Tests and 642 UOContent.Tests**, on Windows and on Linux with **only** `libdeflate0` and `libargon2-1` installed — with the absence of the unversioned symlink asserted first so the run could not pass for the wrong reason. `--check-prereqs` verified in containers on Debian and Alpine across every state that matters: all present, each dependency removed individually, tzdata removed, a deliberately stale `ldconfig` cache, and ICU downgraded to `.so.50` to confirm the floor rejects it. Package resolution and the absence of unversioned symlinks checked on all eight CI distributions. |
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| .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 libargon2 tzdata
Ubuntu, Debian, etc
apt-get update -y
# The ICU runtime package carries the ABI version in its name (libicu74, libicu76, …) and has no
# stable alias, so match it by pattern rather than pinning a release-specific name.
apt-get install -y '^libicu[0-9]+$' libdeflate0 libargon2-1 tzdata
Only the runtime libraries are needed — the -dev/-devel packages are not. Run
./build-tool --check-prereqs to check the current machine and print the exact packages your
release needs.
zstd is not listed because ZstdNet bundles libzstd for every platform, and liburing is not
listed because IORingGroup issues io_uring syscalls directly.
If the shard's configured time zone is a legacy alias such as US/Eastern, Debian 12 and Ubuntu
24.04 also need tzdata-legacy. See Platform Prerequisites
for what each dependency is for and what breaks without it.
OSX Requirements
brew install icu4c libdeflate 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