SignalR connection aborts and doesn't reconnect when downloading a file with firefox.

[bwalendz]

Problem:

I have download links on my page, like <a href="/TestSR/Download">Download</a> and they are powered by an ASP.NET MVC4 action 'Download' on the controller 'TestSR'.

public FileResult Download()
{
   var data = System.Text.Encoding.ASCII.GetBytes("Col1,Col2,Col3,Col4,Col5");
   return File(data, "text/csv", "filename.csv");
}

When one of these is clicked in firefox the SignalR connection is aborted and doesn't reconnect/re-establish. Here is the fidler HTTP log

- Page load
GET https://localhost/realtime/negotiate?clientProtocol=1.4&connectionData=%5B%7B%22name%22%3A%22notificationhub%22%7D%5D&_=1404314258162
GET https://localhost/realtime/connect?transport=serverSentEvents&clientProtocol=1.4&connectionToken=qpX3G8BRx%2BmIDP7HyYsiDPT9hyrGH4Af2NEKlPYm9nzIz3enpE1sWyce5a5WTuAZMIHXWDYt0r9CCw0A1rpwUdfymss57wx7mFDSrz2m6qpaJQppDShXY8nbgkx8k4Ox&connectionData=%5B%7B%22name%22%3A%22notificationhub%22%7D%5D&tid=10
GET https://localhost/realtime/start?transport=serverSentEvents&clientProtocol=1.4&connectionToken=qpX3G8BRx%2BmIDP7HyYsiDPT9hyrGH4Af2NEKlPYm9nzIz3enpE1sWyce5a5WTuAZMIHXWDYt0r9CCw0A1rpwUdfymss57wx7mFDSrz2m6qpaJQppDShXY8nbgkx8k4Ox&connectionData=%5B%7B%22name%22%3A%22notificationhub%22%7D%5D&_=1404314258163

- After clicking <a href="/TestSR/Download">Download</a> in Firefox/36.0
- Download dialog appears
POST https://localhost/realtime/abort?transport=serverSentEvents&clientProtocol=1.4&connectionToken=qpX3G8BRx%2BmIDP7HyYsiDPT9hyrGH4Af2NEKlPYm9nzIz3enpE1sWyce5a5WTuAZMIHXWDYt0r9CCw0A1rpwUdfymss57wx7mFDSrz2m6qpaJQppDShXY8nbgkx8k4Ox&connectionData=%5B%7B%22name%22%3A%22notificationhub%22%7D%5D
GET https://localhost/TestSR/Download

SignalR logs

[11:49:49 GMT-0400 (Eastern Standard Time)] SignalR: Client subscribed to hub 'notificationhub'.
[11:49:49 GMT-0400 (Eastern Standard Time)] SignalR: Negotiating with '/realtime/negotiate?clientProtocol=1.4&connectionData=%5B%7B%22name%22%3A%22notificationhub%22%7D%5D'.
GET https://localhost/realtime/negotiate?clientProtoc...CBUFUp7CejAao5iIWNuEWCkgPPanD281&_=1404316188404
[11:49:49 GMT-0400 (Eastern Standard Time)] SignalR: Attempting to connect to SSE endpoint 'https://localhost/realtime/connect?transport=serverSentEvents&clientProtocol=1.4&connectionToken=m2pSiYpOWuf%2FA6dgP53uZ2BDMpKqbmxw9r%2FkXFOQoOLjlc3azDITptSZcm%2F3RT2zxXxXPLfehQTrJ4NASGWYnFjyTLCi%2FayY2sMFcefwaaCn3Yh7wFWurUTGmz4FhNGX&connectionData=%5B%7B%22name%22%3A%22notificationhub%22%7D%5D&tid=0'.
[11:49:49 GMT-0400 (Eastern Standard Time)] SignalR: EventSource connected.
GET https://localhost/realtime/start?transport=server...CBUFUp7CejAao5iIWNuEWCkgPPanD281&_=1404316188405
[11:49:49 GMT-0400 (Eastern Standard Time)] SignalR: Now monitoring keep alive with a warning timeout of 13333.333333333332 and a connection lost timeout of 20000.
[11:49:54 GMT-0400 (Eastern Standard Time)] SignalR: Stopping connection.
[11:49:54 GMT-0400 (Eastern Standard Time)] SignalR: EventSource calling close().
POST https://localhost/realtime/abort?transport=server...NVzwjiP4wkrw3kqnCBUFUp7CejAao5iIWNuEWCkgPPanD281
[11:49:54 GMT-0400 (Eastern Standard Time)] SignalR: Fired ajax abort async = false.
[11:49:54 GMT-0400 (Eastern Standard Time)] SignalR: Stopping the monitoring of the keep alive.

This does not happen in IE11 or Chrome 35.0.1916.153.

Here is the fidler log from chrome

- Page load
GET https://localhost/realtime/negotiate?clientProtocol=1.4&connectionData=%5B%7B%22name%22%3A%22notificationhub%22%7D%5D&_=1404314679153
GET https://localhost/realtime/connect?transport=serverSentEvents&clientProtocol=1.4&connectionToken=pTsLprS5LAAiMp%2FrEmEdUNMXiTE306HvHQExIquTc%2BVqeMA9GG87VSTwvvJx8yj9UJHVnoqISFtTme69Otwf48xeVDr3Wprg02UYOaADTTdg3CCyBlcZK0u7CQKDJ54y&connectionData=%5B%7B%22name%22%3A%22notificationhub%22%7D%5D&tid=10
GET https://localhost/realtime/start?transport=serverSentEvents&clientProtocol=1.4&connectionToken=pTsLprS5LAAiMp%2FrEmEdUNMXiTE306HvHQExIquTc%2BVqeMA9GG87VSTwvvJx8yj9UJHVnoqISFtTme69Otwf48xeVDr3Wprg02UYOaADTTdg3CCyBlcZK0u7CQKDJ54y&connectionData=%5B%7B%22name%22%3A%22notificationhub%22%7D%5D&_=1404314679154

- Click <a href="/TestSR/Download">Download</a> in Chrome
- Download dialog appears
GET https://localhost/TestSR/Download
GET https://localhost/realtime/reconnect?transport=serverSentEvents&messageId=s-0%2C380C&clientProtocol=1.4&connectionToken=pTsLprS5LAAiMp%2FrEmEdUNMXiTE306HvHQExIquTc%2BVqeMA9GG87VSTwvvJx8yj9UJHVnoqISFtTme69Otwf48xeVDr3Wprg02UYOaADTTdg3CCyBlcZK0u7CQKDJ54y&connectionData=%5B%7B%22name%22%3A%22notificationhub%22%7D%5D&tid=4

[11:52:14 GMT-0400 (Eastern Daylight Time)] SignalR: Client subscribed to hub 'notificationhub'.
[11:52:14 GMT-0400 (Eastern Daylight Time)] SignalR: Negotiating with '/realtime/negotiate?clientProtocol=1.4&connectionData=%5B%7B%22name%22%3A%22notificationhub%22%7D%5D'.
[11:52:14 GMT-0400 (Eastern Daylight Time)] SignalR: Attempting to connect to SSE endpoint 'https://localhost/realtime/connect?transport=serverSentEvents&clientProtoco…Ah0rGI&connectionData=%5B%7B%22name%22%3A%22notificationhub%22%7D%5D&tid=1'.
[11:52:14 GMT-0400 (Eastern Daylight Time)] SignalR: EventSource connected.
[11:52:14 GMT-0400 (Eastern Daylight Time)] SignalR: Now monitoring keep alive with a warning timeout of 13333.333333333332 and a connection lost timeout of 20000.
Resource interpreted as Document but transferred with MIME type text/csv: "https://localhost/TestSR/Download".
[11:52:27 GMT-0400 (Eastern Daylight Time)] SignalR: Keep alive has been missed, connection may be dead/slow. 
[11:52:34 GMT-0400 (Eastern Daylight Time)] SignalR: Keep alive timed out.  Notifying transport that connection has been lost.
[11:52:36 GMT-0400 (Eastern Daylight Time)] SignalR: EventSource calling close(). 
[11:52:36 GMT-0400 (Eastern Daylight Time)] SignalR: serverSentEvents reconnecting.
[11:52:36 GMT-0400 (Eastern Daylight Time)] SignalR: Attempting to connect to SSE endpoint 'https://localhost/realtime/reconnect?transport=serverSentEvents&messageId=s…Ah0rGI&connectionData=%5B%7B%22name%22%3A%22notificationhub%22%7D%5D&tid=7'.
[11:52:36 GMT-0400 (Eastern Daylight Time)] SignalR: EventSource connected. 

I've traced the abort back to this line in jquery.signalR-2.1.0.js line 632:

if (isFirefox11OrGreater) {
    // Firefox does not fire cross-domain XHRs in the normal unload handler on tab close.
    // #2400
    _pageWindow.bind("beforeunload", function () {
        // If connection.stop() runs runs in beforeunload and fails, it will also fail
        // in unload unless connection.stop() runs after a timeout.
        window.setTimeout(function () {
            connection.stop(asyncAbort);
        }, 0);
    });
}

Any advice is appreciated, thanks!

Using:

SignalR: 2.1.0 (redis backplane)
Browsers:
Mozilla/5.0 (Windows NT 6.1; WOW64; rv:30.0) Gecko/20100101 Firefox/30.0
Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/35.0.1916.153 Safari/537.36

JS setup:

$.connection.hub.start();

[DamianEdwards]

It appears that Firefox fires the window beforeunload event when you initiate a file download, and thus we stop the connection. This isn't completely unexpected as it's a navigation. You can work around this yourself by registering a callback for the connection's close event and manually calling start on it again after a short timeout (e.g. 1 sec).

[halter73]

While we are taking a look at the beforeunload event, we should probably look at this issue as well: https://connect.microsoft.com/VisualStudio/feedback/details/817138/browser-link-script-breaks-onbeforeunload-event-in-firefox

[DamianEdwards]

We'll look at this in v3

[arc95]

This is still an issue with FF. In ASP.NET Core 3+, I found the easiest solution is to use the .withAutomaticReconnect() when building the connection (example).