The correct way to create tcp connection to localhost

Question

Created Apr ’21

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Participants 2

Hi there,

I am using NetworkExtension and would like to create tcp connection to localhost. With below code, faced some strange problems: appproxy restart itself periodically with all the traffic during the test.

Code Block import NetworkExtension
let ep = NWHostEndpoint(hostname: "127.0.0.1", port: String(8888))
let connection = createTCPConnection(to: ep, enableTLS: false, tlsParameters: nil, delegate: nil)

Wonder what is the correct way to achieving that?

Thanks in advance for any suggestion.

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Answer 1

Systems Engineer OP

Apple

Apr ’21

appproxy restart itself periodically with all the traffic during the test.

This usually indicates a crash on the Network Extension and indicates an issue in your code. Try adding the following to know for sure:

Code Block swiftfinal class TransparentProxyProvider: NEAppProxyProvider {
    
    static let log = OSLog(subsystem: "com.example.yourbundle_id.TransparentProxy", category: "provider")
    
    override init() {
        self.log = Self.log
        os_log(.debug, log: self.log, "init")
        super.init()
    }
    private let log: OSLog
    /* ... */
}

If you see your constructor being hit when your proxy restarts, then this indicates a crash.

It looks like you are using an in-provider networking class for NWTCPConnection, which is fine in most cases, but it also looks like you are using an NEAppProxyProvider if I understood you correctly, so you do have the flexibility of NWConnection as well. Can you tell me more about why you are using NWTCPConnection?

Matt Eaton
DTS Engineering, CoreOS
meaton3@apple.com

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