Refactor endpoint verification prior to connection

Summary:
^

There's a similar issue/request for Android. So, this change moves the code out from the FlipperKit into Flipper as to be able to reuse it.

Reviewed By: aigoncharov

Differential Revision: D35961745

fbshipit-source-id: aa255db582a7852dc06c2feaba389d1dac3b0f67

xplat/Flipper/FlipperConnectionEndpointVerifier.h

@@ -0,0 +1,20 @@
+/*
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+#pragma once
+
+#include <string>
+
+namespace facebook {
+namespace flipper {
+struct ConnectionEndpointVerifier {
+  /** Verifies whether the given endpoint is listening
+   for incoming connections. */
+  static bool verify(const std::string& host, int port);
+};
+} // namespace flipper
+} // namespace facebook