Handling multiple requests with C# HttpListener

Question

I have a .NET Windows Service which spawns a thread that basically just acts as an HttpListener. This is working fine in synchronous mode example...

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Answer 1

If you're here from the future and trying to handle multiple concurrent requests with a single thread using async/await..

public async Task Listen(string prefix, int maxConcurrentRequests, CancellationToken token)
{
    HttpListener listener = new HttpListener();
    listener.Prefixes.Add(prefix);
    listener.Start();

    var requests = new HashSet<Task>();
    for(int i=0; i < maxConcurrentRequests; i++)
        requests.Add(listener.GetContextAsync());

    while (!token.IsCancellationRequested)
    {
        Task t = await Task.WhenAny(requests);
        requests.Remove(t);

        if (t is Task<HttpListenerContext>)
        {
            var context = (t as Task<HttpListenerContext>).Result;
            requests.Add(ProcessRequestAsync(context));
            requests.Add(listener.GetContextAsync());
        }
    }
}

public async Task ProcessRequestAsync(HttpListenerContext context)
{
    ...do stuff...
}

Answer 2

If you need a more simple alternative to BeginGetContext, you can merely queue jobs in ThreadPool, instead of executing them on the main thread. Like such:

private void CreateLListener() {
    //....
    while(true) {
        ThreadPool.QueueUserWorkItem(Process, listener.GetContext());    
    }
}
void Process(object o) {
    var context = o as HttpListenerContext;
    // process request and make response
}

Answer 3

You need to use the async method to be able to process multiple requests. So you would use e BeginGetContext and EndGetContext methods.

Have a look here.

The synchronous model is appropriate if your application should block while waiting for a client request and if you want to process only one *request at a time*. Using the synchronous model, call the GetContext method, which waits for a client to send a request. The method returns an HttpListenerContext object to you for processing when one occurs.