Enabling a multipathServiceType in NWParameters on iOS 17.x+ breaks establishing peer to peer NWConnections

[Removed] this was an attempt to post the console output from the error above

I tried to add my console output with the network error stack trace for the issue multiple times but the forum keeps deeming it "sensitive" so I'm add it as a .txt here.

Using Multipath TCP in a peer-to-peer app is a bit strange. Most folks only care about MPTCP in the context of Wi-Fi and WWAN.

Regardless, if this previously worked and has broken on iOS 17, you should file a bug about that. Please post your bug number, just for the record.

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Quinn “The Eskimo!” @ Developer Technical Support @ Apple
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Done and done. Feedback ID: FB13401552 (Enabling a multipathServiceType in NWParameters on iOS 17.x+ breaks establishing peer to peer NWConnections)

You're totally right, we originally didn't have it enabled at all. We eventually noticed that with multipath enabled we were getting a faster rate of sending data over the NWConnection using func send(content: Data?, contentContext: NWConnection.ContentContext = .defaultMessage, isComplete: Bool = true, completion: NWConnection.SendCompletion).

FB13401552

Much appreciated.

We eventually noticed that with multipath enabled we were getting a faster rate of sending data

Oh, that’s interesting. I suspect that MPTCP allows seamless switching between the peer-to-peer Wi-Fi interface and the infrastructure Wi-Fi interface. That’s cool, and it should speed things up because the infrastructure Wi-Fi interface is faster.

However, that’s really just a guess. You’d need to look at a packet trace to tell for sure.

Regardless, disabling MPTCP is an easy workaround.

Share and Enjoy
—
Quinn “The Eskimo!” @ Developer Technical Support @ Apple
let myEmail = "eskimo" + "1" + "@" + "apple.com"