NWListener stops receiving incoming connections after a minute

Question

I am listening to DLNA notifications over TCP and for about a minute, my NWListener instance keeps receiving new notifications but after about a minute, it stops getting the notifications. NWListener is still alive at that point and the DLNA subscription is valid as well. No such issues when listening using GCDWebserver. Am I missing something obvious with NWListener?

Network

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Posted by

laszloxgergely

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Answer 1

after about a minute, it stops getting the notifications.

What platform are you testing this on?

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

Posted by

eskimo

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Answer 2

iOS (16/17) and macCatalyst, same behaviour in each case.

Posted by

laszloxgergely

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Answer 3

I can’t think of anything that would cause a TCP NWListener to stop listening after 60 seconds on a Mac. I tested this here in my office and didn’t see the behaviour you’re reporting. Specifically:

Using Xcode 14.3 on macOS 13.4.1 (hey, I’m up-to-date for once!) I created a new test project from the macOS > App template.
In Signing & Capabilities, I disabled the App Sandbox.

I modified applicationDidFinishLaunching(_:) as follows:

var listener: NWListener!

func applicationDidFinishLaunching(_ aNotification: Notification) {
    let listener = try! NWListener(using: .tcp, on: 12345)
    listener.stateUpdateHandler = { newState in
        print("\(Date.now): did change state, new: \(newState)")
    }
    listener.newConnectionHandler = { newConnection in
        print("\(Date.now): did receive connection, dropping")
    }
    listener.start(queue: .main)
    self.listener = listener
}

I ran the app, resulting in this output:

2023-06-30 08:34:28 +0000: did change state, new: ready

In Terminal, I connected to my app’s server:

% nc localhost 12345

resulting in this output:

2023-06-30 08:34:32 +0000: did receive connection, dropping

I waited two minutes and repeated the previous step; here’s what I got:
```
2023-06-30 08:36:45 +0000: did receive connection, dropping
```

I’m not sure why you’re seeing this problem but my advice is:

Repeat the above process, just to rule out environmental issues.
Integrate my listener code into your real app and see if it has the problem there.

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

Posted by

eskimo

All works as expected when using the nc command, however when listening to the DLNA notifications NWListener still stops receiving them after a minute or so. No such issues with a GCDWebserver based listener so I have to use that for now.

—
laszloxgergely

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NWListener stops receiving incoming connections after a minute

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