swift – iOS Socket.IO client connects but events don’t reach server (auth via headers, works on Android/Postman)

Description:
I’m implementing a Socket.IO connection in an iOS app using socket.io-client-swift. The backend uses authentication via headers (user-id and sessionkey). The issue I’m facing is:

The client appears to connect successfully, even with invalid headers.

However, the server never receives the emitted events, nor does it respond with any data.

On Android/Postman, the socket connects but disconnects immediately if the auth headers are invalid — which is expected and correct.

On iOS, the socket stays connected even with wrong headers, but behaves like a “phantom connection” — no event delivery, no server response.

SocketManager Code (Note: This was generated by ChatGPT, I had one which I made but after 2 days of debugging and repetitions this is what I have landed on)

import SocketIO

final class SocketManager {

    static let shared = SocketManager()

    private var manager: SocketIO.SocketManager?   
    private var socket: SocketIOClient?            

    private init() {}

    func connect(
        userId: String,
        sessionKey: String,
        onMessageReceived: @escaping ([String: Any]) -> Void,
        onSenderMessage: @escaping ([String: Any]) -> Void
    ) {
        guard let url = URL(string: " else {
            print("Invalid URL")
            return
        }

        let config: SocketIOClientConfiguration = [
            .log(true),
            .compress,
            .extraHeaders([
                "user-id": "\(userId)",
                "sessionkey": sessionKey
            ]),
            .forceNew(true),
            .reconnects(true)
        ]
        self.manager = SocketIO.SocketManager(socketURL: url, config: config)
        self.socket = self.manager?.defaultSocket

        guard let socket = self.socket else { return }

        socket.on(clientEvent: .connect) { data, ack in
            print("Socket connected")
        }

        socket.on("receiver-message") { data, _ in
            guard let json = data.first as? [String: Any] else { return }
            onMessageReceived(json)
        }

        socket.on("sender-message") { data, _ in
            guard let json = data.first as? [String: Any] else { return }
            onSenderMessage(json)
        }

        socket.on(clientEvent: .disconnect) { _, _ in
            print("Socket disconnected")
        }

        socket.on(clientEvent: .error) { data, _ in
            print("Socket error", data)
        }

        socket.connect()
    }

    func sendMessage(messageData: [String: Any]) {
        guard socket?.status == .connected else {
            print("Socket not connected. Message not sent.")
            return
        }
        socket?.emit("sendMessage", messageData)
    }

    func disconnect() {
        socket?.disconnect()
    }
}

I’ve tried multiple configurations and approaches for last 2 days.