ModernUO Emulator
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**Follow-on to #2639 (merged). References a local IORingGroup `1.0.13-preview.11` pack until 1.0.13 (modernuo/IORingGroup#15) is published; do not merge before that switch.** ## Summary Consumes IORingGroup's lean base pools (modernuo/IORingGroup#15): both network pools now start with one slab, grow a slab at a time with the population, and trim idle slabs back after quiet periods. - Fixes the transport's send-pool cap: previously only 1024 of the 4096 connections could get a send buffer; connection 1025 was closed at accept. - Network memory at boot drops from about 96 MB to about 10 MB at the defaults; a full 4096 logged-in connections is about 1.25 GB of base buffers plus the growth budget. - New settings: `network.initialBufferSlabs` (default 1; slabs of each pool held from boot and the trim floor) and `network.maxBufferSlabs` (default 128; divides the connection maximum into slabs, 32 connections per slab). Both are coerced with a warning; the same value feeds the ring table and the manager so they cannot drift. - The Debug-only maintenance line includes base-pool capacity and releases. - `dev-docs/server-requirements.md` rewrites the network memory story and adds the two settings. ## Pre-auth buffers Every connection starts on the transport's platform-minimum buffers (4 KB receive, 4 KB send) instead of the base pools. It is promoted to full-size buffers (64 KB receive, `network.sendBufferSize` send) when the game server verifies its account — the point where `NetState.Account` is assigned in the `GameServer_AwaitingGameServerLogin` or `GameServer_LoggedIn` state, so a verdict that lands after the parser has moved on still promotes. Nothing ever moves back. The login-server pass stays on the small buffers for its whole lifetime. Before credentials verify, nothing promotes: the 4 KB send ring is the entire pre-auth send budget, and a connection that overruns it is dropped as exhausted, exactly as the receive side drops a packet header declaring more bytes than the receive buffer can hold (new guard in `HandlePacket`; it also closes the old 65535-byte edge on 64 KB buffers). The stock login sequence sends under 2 KB. After credentials verify, the send path promotes on demand if it ever needs to (unbudgeted, outside the memory ceiling and the shrink bookkeeping — promotion is not growth), and the oversize-packet guard waits on a pending receive promotion or retries a stalled one once for a verified account before disconnecting. A completion that fills the receive buffer arms no receive, so `HandleReceive` now calls `RingSocket.ResumeReceive()` after the parse loop — at 4 KB a burst of small packets fills the buffer in one completion. Net effect: a flood of unauthenticated connections tops out at about 32 MB across the full 4096-connection cap where the platform minimum is 4 KB (the transport's retained slabs and the base pools used by logged-in players are separate), and never allocates a base-pool slab. Platform note: on Windows Server 2012 R2 / 2016 the transport's legacy mapping path floors at 64 KB: the pre-auth receive pool is off there (its base is 64 KB), while the pre-auth send buffer starts at 64 KB under the 256 KB base. The server logs the effective sizes at startup. ## Testing Server.Tests (905) and UOContent.Tests green on the preview pack (one pre-existing `FamiliarAITests` failure from #2644 reproduces on `main`, tracked separately). New tests cover both coercions, that the ring's registration table equals `RequiredRegisteredBuffers` for the configured values, promotion on game-server auth and on a late account, no promotion on the login server, pre-credential overrun ending in exhaustion, post-credential on-demand promotion, the oversize-packet guard through loopback (error, wait, retry with an account, and a promotion made pending mid-parse), and receiving again after a burst fills the initial buffer. |
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| branding | ||
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| 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 | ||
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| version.json | ||
ModernUO 
Ultima Online Server Emulator for the modern era!
Requirements
Supported Operating Systems
Required Frameworks
All Operating Systems
Windows
Hardware
| Use | vCPU | RAM | Storage |
|---|---|---|---|
| Development / test | 2 dedicated | 2 GB | SSD |
| Small live shard (< 50 concurrent) | 4 dedicated | 4 GB | NVMe |
| Medium (50–200) | 4–8 | 8 GB | NVMe |
| Large (200+) | 8+, high clock | 16 GB+ | NVMe |
See dev-docs/server-requirements.md for more information.
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