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HttpListener does not respond

Started by R.Ganesh, Mar 01 2012 06:20 PM

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3 replies to this topic

#1 R.Ganesh

Member

Members
12 posts

LocationSwitzerland

Posted 01 March 2012 - 06:20 PM

Hi all,

I have a web server running on an Netduino plus using the HttpListener listening for client requests and responding with a simple html. I am investigating a problem at a project installation, where the web server stops responding after few days of working (client requests are not so often, once in a day or even longer). I tried to reproduce the problem but did not succeed. However, during testing I noticed that one way to make the web server non-responsive is to send a burst of requests - i did this by keeping F5 key pressed in the internet explorer (continously refereshes). After this, the web server stops responding. First, the code (simplified):

internal static void RunServer()
        {
            HttpListener listener = new HttpListener("http", -1);
            listener.Start();

            while (true)
            {
                try
                {
                    Debug.Print("Listening..");
                    HttpListenerContext context = null;
                    context = listener.GetContext();
                    Debug.Print("Received request from " +  context.Request.UserHostAddress.ToString());
                    context.Response.ContentType = "text/html";
                    string html = "<html><p>Hello World " + DateTime.Now.ToString() + "</p></html>";
                    System.Text.UTF8Encoding encoding = new System.Text.UTF8Encoding();
                    byte[] messageBody = encoding.GetBytes(html);
                    context.Response.OutputStream.Write(messageBody, 0, messageBody.Length);

                    if (context.Response != null)
                        context.Response.Close();
                }
                catch (Exception e)
                {
                    Debug.Print("Exception occured! " + e.Message);

                    PowerState.RebootDevice(true, 1000);
                }
            }
        }

Next, the version information:

.NetMF v4.1.2821.0
NetduinoPlus, Build Date:Mar 26 2011 02:15:31
ARM Compiler version 400902
TinyCLR (Build 4.1.2821.0)

Finally, the exception (as seen on MF Deploy console)

Listening..
#### Exception System.Net.Sockets.SocketException - CLR_E_FAIL (5) ####
#### Message:
#### Microsoft.SPOT.Net.SocketNative::accept [IP: 0000] ####
#### System.Net.Sockets.Socket::Accept [IP: 001c] ####
#### System.Net.HttpListener::AcceptThreadFunc [IP: 0020] ####
#### SocketException ErrorCode = 10056
Received request from 4.0.0.0
#### Exception System.Net.Sockets.SocketException - CLR_E_FAIL (4) ####
#### Message:
#### Microsoft.SPOT.Net.SocketNative::send [IP: 0000] ####
#### System.Net.Sockets.Socket::Send [IP: 0018] ####
#### System.Net.Sockets.NetworkStream::Write [IP: 0051] ####
#### System.Net.OutputNetworkStreamWrapper::Write [IP: 0017] ####
#### System.Net.HttpListenerResponse::SendHeaders [IP: 0021] ####
#### System.Net.OutputNetworkStreamWrapper::Write [IP: 000d] ####
#### NetduinoTest.WebServer::RunServer [IP: 0074] ####
#### SocketException ErrorCode = 10056
Exception occured! Exception was thrown: System.Net.Sockets.SocketException

Any pointers on this would be really helpful to me! Thank you!

Ganesh

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#2 GlenS

Member

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23 posts

LocationTamworth, UK

Posted 01 March 2012 - 11:30 PM

Ganesh, I haven't had the time to do any in-depth stdy, but what I think you may be seeing is the result of HTTP requests overlapping. Some quick testing I did was everythign seemed to work if I was slow in hitting the F5 refresh in Firefox, but if I hit it very quickly I hit the error you describe very quickly. Take a look at the code from Jasper Schuurmans at : http://www.schuurman...lus#comment-256 He has an excelent multi-threaded web server that you could adapt to your needs. I have used it in one of my demo projects without any issues once I had fixed a small issue he had in the code that did not return a complete HTTP header in the response. This was causing the response to fail on some mobile devices. Hope this helps Glen

Giuliano likes this

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#3 R.Ganesh

Member

Members
12 posts

LocationSwitzerland

Posted 13 April 2012 - 03:43 PM

Hi Glen, I tried using the multi-threaded variant, but no luck.. seems like a low level socket exception brings down the connectivity and is not recovered until a reset is done.. Cheers! Ganesh

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#4 OZ8ET

Advanced Member

Members
72 posts

LocationHundested, Denmark

Posted 21 August 2012 - 05:08 AM

Hi
I use a socket-based server and get the same problem. It is very easy to reproduce. Just hit the F5 on the browser a couple of times and you get the Socket Exception.

With the socket-based server, it looks like it recovers after the exception - I have not tried it for a long perode of time yet.

This is what it looks like:

		public HttpSession(int Port = 80, WebRequest userRequester = null)
		{
			_userRequester = userRequester;
			_socket = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);
			_socket.Bind(new IPEndPoint(IPAddress.Any, Port));
			new Thread(_Listen).Start();
		}

		private void _Listen()
		{
			_socket.Listen(10);
			while (true)
			{
				try
				{
					using (Socket client = _socket.Accept())
					{
						int _requestSize;
						byte[] _buffer;
						int _amountRead;
						Request _request;

						_requestSize = client.Available;
						_buffer = new byte[Settings.bufLen];
						_amountRead = client.Receive(_buffer, Settings.bufLen, SocketFlags.None);
						_request = new Request(client, _buffer);
						_buffer = null;
						if (_userRequester != null) _userRequester(_request); else _defaultRequester(_request);
						_request = null;
						Debug.GC(true);
					}
				}
				catch (Exception ex) { 
					Debug.Print(ex.Message);
					//PowerState.RebootDevice(false, 1000); 
				}
				Thread.Sleep(10);
			}
		}

The latest change I made was to move the statement "_socket.Listen(10);" from the sub HttpSession() to the sub _Listen().
For some unexplainable (for me!) reasoen, it made the thing recover after the exception rather than stopping the server.

This is with 4.1 - when (if!) 4.2 is relesed and when (if!) OneWire becomes available for 4.2, I look forward to see if this has been solved in 4.2.

Regards
Erik