Replace NEKit dependency with reduced subset

GlassVPN/zhuhaow-NEKit/Socket/AdapterSocket/DirectAdapter.swift

@@ -0,0 +1,48 @@
+import Foundation
+
+/// This adapter connects to remote directly.
+public class DirectAdapter: AdapterSocket {
+    /// If this is set to `false`, then the IP address will be resolved by system.
+    var resolveHost = false
+
+    /**
+     Connect to remote according to the `ConnectSession`.
+
+     - parameter session: The connect session.
+     */
+    override public func openSocketWith(session: ConnectSession) {
+        super.openSocketWith(session: session)
+
+        guard !isCancelled else {
+            return
+        }
+
+        do {
+            try socket.connectTo(host: session.host, port: Int(session.port), enableTLS: false, tlsSettings: nil)
+        } catch let error {
+            observer?.signal(.errorOccured(error, on: self))
+            disconnect()
+        }
+    }
+
+    /**
+     The socket did connect to remote.
+
+     - parameter socket: The connected socket.
+     */
+    override public func didConnectWith(socket: RawTCPSocketProtocol) {
+        super.didConnectWith(socket: socket)
+        observer?.signal(.readyForForward(self))
+        delegate?.didBecomeReadyToForwardWith(socket: self)
+    }
+
+    override public func didRead(data: Data, from rawSocket: RawTCPSocketProtocol) {
+        super.didRead(data: data, from: rawSocket)
+        delegate?.didRead(data: data, from: self)
+    }
+
+    override public func didWrite(data: Data?, by rawSocket: RawTCPSocketProtocol) {
+        super.didWrite(data: data, by: rawSocket)
+        delegate?.didWrite(data: data, by: self)
+    }
+}