Almost there

Author: piercifani

Package.swift

@@ -1,4 +1,4 @@
-// swift-tools-version:5.9
+// swift-tools-version:6.0
 
 import PackageDescription
 
@@ -19,5 +19,6 @@ let package = Package(
     targets: [
         .target(name: "SocketIO", dependencies: ["Starscream"]),
         .testTarget(name: "TestSocketIO", dependencies: ["SocketIO"]),
-    ]
+    ],
+    swiftLanguageModes: [.v6]
 )

Source/SocketIO/Ack/SocketAckEmitter.swift

@@ -132,11 +132,11 @@ public final class OnAckCallback: NSObject {
         socket.emit(items, ack: ackNumber, binary: binary)
 
         guard seconds != 0 else { return }
-
+        let _ackNumber = ackNumber
         socket.manager?.handleQueue.asyncAfter(deadline: DispatchTime.now() + seconds) {[weak socket] in
             guard let socket = socket else { return }
 
-            socket.ackHandlers.timeoutAck(self.ackNumber)
+            socket.ackHandlers.timeoutAck(_ackNumber)
         }
     }
 

Source/SocketIO/Client/SocketIOClient.swift

@@ -40,7 +40,7 @@ import Foundation
 ///
 /// **NOTE**: The client is not thread/queue safe, all interaction with the socket should be done on the `manager.handleQueue`
 ///
-open class SocketIOClient: NSObject, SocketIOClientSpec {
+open class SocketIOClient: NSObject, SocketIOClientSpec, @unchecked Sendable {
     // MARK: Properties
 
     /// The namespace that this socket is currently connected to.
@@ -122,7 +122,7 @@ open class SocketIOClient: NSObject, SocketIOClientSpec {
     /// - parameter timeoutAfter: The number of seconds after which if we are not connected we assume the connection
     ///                           has failed. Pass 0 to never timeout.
     /// - parameter handler: The handler to call when the client fails to connect.
-    open func connect(withPayload payload: [String: Any]? = nil, timeoutAfter: Double, withHandler handler: (() -> ())?) {
+    open func connect(withPayload payload: [String: Any]? = nil, timeoutAfter: Double, withHandler handler: (@Sendable () -> ())?) {
         assert(timeoutAfter >= 0, "Invalid timeout: \(timeoutAfter)")
 
         guard let manager = self.manager, status != .connected else {

Source/SocketIO/Client/SocketIOClientSpec.swift

@@ -77,7 +77,7 @@ public protocol SocketIOClientSpec : AnyObject {
     /// - parameter timeoutAfter: The number of seconds after which if we are not connected we assume the connection
     ///                           has failed. Pass 0 to never timeout.
     /// - parameter handler: The handler to call when the client fails to connect.
-    func connect(withPayload payload: [String: Any]?, timeoutAfter: Double, withHandler handler: (() -> ())?)
+    func connect(withPayload payload: [String: Any]?, timeoutAfter: Double, withHandler handler: (@Sendable() -> ())?)
 
     /// Called when the client connects to a namespace. If the client was created with a namespace upfront,
     /// then this is only called when the client connects to that namespace.

Source/SocketIO/Engine/SocketEngine.swift

@@ -32,7 +32,7 @@ import FoundationNetworking
 /// The class that handles the engine.io protocol and transports.
 /// See `SocketEnginePollable` and `SocketEngineWebsocket` for transport specific methods.
 open class SocketEngine: NSObject, WebSocketDelegate, URLSessionDelegate,
-                         SocketEnginePollable, SocketEngineWebsocket, ConfigSettable {
+                         SocketEnginePollable, SocketEngineWebsocket, ConfigSettable, @unchecked Sendable {
 
 
     // MARK: Properties

Source/SocketIO/Engine/SocketEnginePacketType.swift

@@ -26,7 +26,7 @@
 import Foundation
 
 /// Represents the type of engine.io packet types.
-public enum SocketEnginePacketType: Int {
+public enum SocketEnginePacketType: Int, Sendable {
     /// Open message.
     case open
 

Source/SocketIO/Engine/SocketEnginePollable.swift

@@ -119,7 +119,7 @@ extension SocketEnginePollable {
         doLongPoll(for: req)
     }
 
-    func doRequest(for req: URLRequest, callbackWith callback: @escaping (Data?, URLResponse?, Error?) -> ()) {
+    func doRequest(for req: URLRequest, callbackWith callback: @escaping (@Sendable(Data?, URLResponse?, Error?) -> ())) {
         guard polling && !closed && !invalidated && !fastUpgrade else { return }
 
         DefaultSocketLogger.Logger.log("Doing polling \(req.httpMethod ?? "") \(req)", type: "SocketEnginePolling")

Source/SocketIO/Engine/SocketEngineSpec.swift

@@ -30,7 +30,7 @@ import FoundationNetworking
 #endif
 
 /// Specifies a SocketEngine.
-public protocol SocketEngineSpec: AnyObject {
+public protocol SocketEngineSpec: AnyObject, Sendable {
     // MARK: Properties
 
     /// The client for this engine.

Source/SocketIO/Manager/SocketManager.swift

@@ -45,7 +45,7 @@ import Foundation
 ///
 /// **NOTE**: The manager is not thread/queue safe, all interaction with the manager should be done on the `handleQueue`
 ///
-open class SocketManager: NSObject, SocketManagerSpec, SocketParsable, SocketDataBufferable, ConfigSettable {
+open class SocketManager: NSObject, SocketManagerSpec, SocketParsable, SocketDataBufferable, ConfigSettable, @unchecked Sendable {
     private static let logType = "SocketManager"
 
     // MARK: Properties
@@ -95,16 +95,16 @@ open class SocketManager: NSObject, SocketManagerSpec, SocketParsable, SocketDat
     public var nsps = [String: SocketIOClient]()
 
     /// If `true`, this client will try and reconnect on any disconnects.
-    public var reconnects = true
+    public var reconnects: Bool = true
 
     /// The minimum number of seconds to wait before attempting to reconnect.
-    public var reconnectWait = 10
+    public var reconnectWait: Int = 10
 
     /// The maximum number of seconds to wait before attempting to reconnect.
-    public var reconnectWaitMax = 30
+    public var reconnectWaitMax: Int = 30
 
     /// The randomization factor for calculating reconnect jitter.
-    public var randomizationFactor = 0.5
+    public var randomizationFactor: Double = 0.5
 
     /// The status of this manager.
     public private(set) var status: SocketIOStatus = .notConnected {

Source/SocketIO/Util/SocketLogger.swift

@@ -68,8 +68,8 @@ public extension SocketLogger {
     }
 }
 
-class DefaultSocketLogger : SocketLogger {
-    static var Logger: SocketLogger = DefaultSocketLogger()
+final class DefaultSocketLogger : SocketLogger, Sendable {
+    static nonisolated(unsafe) var Logger: SocketLogger = DefaultSocketLogger()
 
-    var log = false
+    nonisolated(unsafe) var log = false
 }