From b4c82165c6ca87365cbbafd6de00f1ee887cab39 Mon Sep 17 00:00:00 2001
From: sta <sta.blockhead@gmail.com>
Date: Wed, 26 May 2021 16:53:48 +0900
Subject: [PATCH] [Modify] Lock it

---
 websocket-sharp/Net/HttpListener.cs | 12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)

diff --git a/websocket-sharp/Net/HttpListener.cs b/websocket-sharp/Net/HttpListener.cs
index ac8c0949..a59ae336 100644
--- a/websocket-sharp/Net/HttpListener.cs
+++ b/websocket-sharp/Net/HttpListener.cs
@@ -822,14 +822,16 @@ namespace WebSocketSharp.Net
         throw new ArgumentException (msg, "asyncResult");
       }
 
-      if (ares.EndCalled) {
-        var msg = "This IAsyncResult instance cannot be reused.";
+      lock (ares.SyncRoot) {
+        if (ares.EndCalled) {
+          var msg = "This IAsyncResult instance cannot be reused.";
 
-        throw new InvalidOperationException (msg);
+          throw new InvalidOperationException (msg);
+        }
+
+        ares.EndCalled = true;
       }
 
-      ares.EndCalled = true;
-
       if (!ares.IsCompleted)
         ares.AsyncWaitHandle.WaitOne ();