From ff6cd140cde5d1d519446c0a478e04f58b9a97b2 Mon Sep 17 00:00:00 2001
From: Thom de Jong <t.dejong@tools4ever.com>
Date: Mon, 30 Sep 2019 15:22:09 +0200
Subject: [PATCH] Only close destination when websocket is still open or
 capable of handling the close message

---
 .../Middleware/WebSocketsProxyMiddleware.cs     | 17 ++++++++++++++++-
 1 file changed, 16 insertions(+), 1 deletion(-)

diff --git a/src/Ocelot/WebSockets/Middleware/WebSocketsProxyMiddleware.cs b/src/Ocelot/WebSockets/Middleware/WebSocketsProxyMiddleware.cs
index 6d56a4899..b35a1894e 100644
--- a/src/Ocelot/WebSockets/Middleware/WebSocketsProxyMiddleware.cs
+++ b/src/Ocelot/WebSockets/Middleware/WebSocketsProxyMiddleware.cs
@@ -44,9 +44,24 @@ private static async Task PumpWebSocket(WebSocket source, WebSocket destination,
                 }
                 catch (OperationCanceledException)
                 {
-                    await destination.CloseOutputAsync(WebSocketCloseStatus.EndpointUnavailable, null, cancellationToken);
+                    if (destination.State == WebSocketState.Open || destination.State == WebSocketState.CloseReceived)
+                    {
+                        await destination.CloseOutputAsync(WebSocketCloseStatus.EndpointUnavailable, null, cancellationToken);
+                    }
                     return;
                 }
+                catch (WebSocketException e)
+                {
+                    if (e.WebSocketErrorCode == WebSocketError.ConnectionClosedPrematurely)
+                    {
+                        if (destination.State == WebSocketState.Open || destination.State == WebSocketState.CloseReceived)
+                        {
+                            await destination.CloseOutputAsync(WebSocketCloseStatus.EndpointUnavailable, null, cancellationToken);
+                        }
+                        return;
+                    }
+                    throw;
+                }
 
                 if (result.MessageType == WebSocketMessageType.Close)
                 {