If you've been casually following ReactOS over the years, you'll know the vibe: it's an ambitious "open-source Windows" project that's been building toward better Windows compatibility one hard-earned milestone at a time. And lately, ReactOS has been stacking wins faster than usual.

After recent progress like improved Windows NT 6 compatibility and smoothing out a pretty irritating usability issue, the project has now landed something that can seriously change the day-to-day feel of the system: a major networking performance upgrade.

The Change: Asynchronous TCP Connections Are Finally Here

The headline improvement is this: ReactOS now supports asynchronous (non-blocking) TCP connections thanks to newly merged code.

That sounds technical, but the impact is very practical. A lot of everyday applications rely on TCP networking, and they benefit hugely when the OS can handle connections without forcing the app to "wait" in a blocking way. In real-world terms, this is the kind of fix that can make network-heavy apps feel snappier and more responsive.

ReactOS developers celebrated the merge publicly, pointing out that users should expect noticeable performance improvements in networking applications such as:

Why This Matters: Blocking vs Non-Blocking Isn't Just an Edge Case

Networking performance isn't only about raw bandwidth. A lot of it comes down to how efficiently the operating system handles many small events happening at once: connecting, waiting for data, sending packets, timing out, retrying, and juggling multiple sockets.

When async TCP support is missing or broken, apps can still "work," but they're often forced into less efficient patterns. That can lead to sluggishness, weird stalls, and generally slower behavior under load, especially in apps that open multiple simultaneous connections (which is basically everything modern, from browsers to updaters).

So this isn't a tiny internal tweak. It's one of those foundational fixes that can lift the performance ceiling across a whole category of software.

A Decade in the Making

What makes this milestone more satisfying is how long it's been brewing.

The underlying problem goes back to at least 2016, when a tracking issue was opened about socket connections in non-blocking mode not behaving correctly. That's a core capability that many Windows applications assume exists, so it's the kind of issue that can quietly limit compatibility and performance for years.

According to the project's timeline, multiple pull requests attempted to address it, went through reworks, and evolved over time. And now, after all that iteration, the async connection support patch has finally been merged into the main development code.

What You'll Likely Feel as a User

ReactOS is still a development-focused OS, so it's not like everyone is daily-driving it for work. But for testers, hobbyists, and anyone evaluating it for Windows-like compatibility, this could be one of those changes you immediately notice.

The biggest improvements should show up in scenarios like:

Even if you never think about TCP at all, you'll feel it indirectly as "less waiting" and "fewer stalls" in apps that rely on network activity.

Bigger Picture: ReactOS Momentum Is Building

This networking upgrade also fits a pattern: ReactOS has been ticking off foundational improvements that move it closer to behaving the way Windows-targeted software expects. Compatibility boosts, usability fixes, and now networking performance upgrades all point in the same direction.

In open-source OS development, the big wins often come from solving these deep, unglamorous system-level issues. And this one—an async TCP merge after a 10-year wait—is exactly the kind of milestone that can unlock a lot of progress all at once.

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