A bug in macOS Sequoia 15.0’s firewall could have been disastrous for FarPlay. But we found a way to keep the music going.

When we got the first report that FarPlay app failed to connect after upgrading to Sequoia 15.0, we checked the logs and found that most users who upgraded hadn’t experienced issues, so we thought it might be a one-off case. But after receiving several more complaints it became clear: we had a problem.

FarPlay is an app that allows musicians to make music online interactively. This requires much lower latency than common audio/video conferencing apps provide. To make online jamming feel like you’re in the same room, end-to-end latency needs to be below 20-30ms. That’s why FarPlay relies exclusively on peer-to-peer (P2P) technology. It allows us to use the shortest and the fastest possible path to deliver audio data from one side to another. But P2P connectivity depends strongly on firewall behavior. Firewalls that are too restrictive or incorrectly configured can easily make P2P connections impossible.

Shortly after Apple released macOS Sequoia 15.0, reports of issues with different firewall and network software began popping up. Customers of large security software companies like CrowdStrike, ESET, and SentinelOne reported issues. Some VPNs stopped working too. For some FarPlay users, it looked as though their firewalls just started blocking audio traffic entirely even when their firewalls were turned off completely in system settings. At the same time, others didn’t experience any issues. I was not able to reproduce the problem on my test Mac.

We are a very small company, just a few people. If IT security giants couldn’t solve the issue, what could we do? About 60% of our users are on Mac, and even if only 10% were affected, it could have been disastrous for us. When P2P connectivity is broken, FarPlay simply can’t work. A music teacher can’t provide a scheduled lesson. Musicians can’t conduct their final rehearsal before a concert.

We began researching the changes in the new version of macOS and discovered that the new “Local Network” section in the “Privacy & Security” settings affects FarPlay connectivity. This setting has existed in iOS for a while and has now been added to macOS. Normally, it would only be required for connecting FarPlay clients within the same local network. However, we found that enabling this setting for the FarPlay app also resolved the connectivity issues for users affected by the Sequoia firewall problem.

So, if you have a networking issue with Sequoia, check out the Local Network section of Privacy & Security settings. I can’t say if this helps with other Sequoia issues, but it was a lifesaver for us. Shortly after we published this workaround on our support forum, other users confirmed that it worked for them as well.

Just recently, Apple released Sequoia bugfix version 15.0.1. As usual, its description is vague, it says it “improves compatibility with third-party security software”. We don’t have enough data yet to say if our problem was fixed with this update. Our users already had a solution at that point.

—Anton