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Editorial Team
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Asked: 2026-05-29T09:15:33+00:00

I am trying to do long polling with an HttpWebRequest object. In my C#

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I am trying to do “long polling” with an HttpWebRequest object.

In my C# app, I am making an HTTP GET request, using HttpWebRequest. And then afterwards, I wait for the response with beginGetResponse(). I am using ThreadPool.RegisterWaitForSingleObject to wait for the response, or to timeout (after 1 minute).

I have set the target web server to take a long time to respond. So that, I have time to disconnect the network cable.

After sending the request, I pull the network cable.

Is there a way to get an exception when this happens? So I don’t have to wait for the timeout?

Instead of an exception, the timeout (from RegisterWaitForSingleObject) happens after the 1 minute timeout has expired.

Is there a way to determine that the network connection went down? Currently, this situation is indistinguishable from the case where the web server takes more than 1 minute to respond.

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1 Answer

  1. Editorial Team

    I found a solution:

    Before calling beginGetResponse, I can call the following on the HttpWebRequest:

    req.ServicePoint.SetTcpKeepAlive( true, 10000, 1000)

    I think this means that after 10 seconds of inactivity, the client will send a TCP “keep alive” over to the server. That keep alive will fail if the network connection is down because the network cable was pulled.

    So, when the cable is pulled, I a keep alive gets sent within 10 seconds (at most), and then the callback for BeginGetResponse happens. In the callback, I get and exception when I call req.EndGetResponse().

    I guess this defeats one of the benefits of long polling, though. Since we’re still sending packets around.

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