Highly Performant & Scalable Ultima Online Server Emulator
https://www.modernuo.com
c-sharpcsharpcsharp-coredotnetdotnet-coreemulatorgplgplv3mmommo-enginemmorpgmmorpg-serveronlinerpgrunuoserverservuoultimaultima-onlineuo
Core now owns the question -- "should this socket be denied?" -- and none of the answers. The firewall was the last implementation left in core, and the reasons to keep it did not survive scrutiny: it is not extended downstream, and a shard running bare core has no way to populate it anyway, since the admin gump and the commands that mutate it are both content. Larger shards front the server with an upstream proxy or edge scrubbing and never use it; it survives as the fallback an admin reaches for over a single player, which is squarely content's concern. Nothing about the firewall changes for operators: same Server.Network namespace, same Configuration/firewall.json, same gump and commands, same legacy .cfg migration. It reaches the accept path through ConnectionFilters like any other filter, and registers itself first because an empty set is the cheapest gate. Untangling core from the firewall entry types first: - NetworkUtilities built its reserved-network tables out of CidrFirewallEntry, which made core depend on the firewall for something with nothing to do with banning. Those are constant CIDR blocks answering "is this address in one of these ranges?", so they are now a SortedRangeIndex<UInt128> -- the same primitive the firewall and blocklist already share. Same semantics, same public API, one linear scan replaced by a binary search. - The CIDR -> normalized range parse those tables needed is now IPAddressUtility.TryParseCidrRange, and CidrFirewallEntry drops its private copy of that logic in favor of it. Core no longer references IFirewallEntry or Firewall anywhere. 1344 tests pass. Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com> |
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| AGENTS.md | ||
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| FAQ.md | ||
| GEMINI.md | ||
| global.json | ||
| LICENSE | ||
| ModernUO.slnx | ||
| publish.cmd | ||
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| publish.sh | ||
| README.md | ||
| rider-settings.zip | ||
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| SPONSORS.md | ||
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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