Cobra freezed until SocketException is thrown

Jack2 · March 23, 2012, 6:28am

Hi!

I am doing http request.


HttpWebRequest request = (HttpWebRequest) HttpWebRequest.Create(url);
HttpWebResponse response = (HttpWebResponse) request.GetResponse();

Cobra is connected with cable to router which does not have internet connection.
Unfortunately until exception below is thrown Cobra is not responding at all - is freezed.


    #### Exception System.Net.Sockets.SocketException - CLR_E_FAIL (37) ####
    #### Message: 
    #### Microsoft.SPOT.Net.SocketNative::getaddrinfo [IP: 0000] ####
    #### System.Net.Dns::GetHostEntry [IP: 0008] ####
    #### System.Net.HttpWebRequest::EstablishConnection [IP: 00e1] ####
    #### System.Net.HttpWebRequest::SubmitRequest [IP: 0013] ####
    #### System.Net.HttpWebRequest::GetResponse [IP: 000c] ####
    #### N.Net.MailNotify+SendMesageRequest::Send [IP: 004d] ####
    #### SocketException ErrorCode = -1
    #### Exception System.Net.Sockets.SocketException - CLR_E_FAIL (39) ####
    #### Message: 
    #### Microsoft.SPOT.Net.SocketNative::getaddrinfo [IP: 0000] ####
    #### System.Net.Dns::GetHostEntry [IP: 0008] ####
    #### System.Net.HttpWebRequest::EstablishConnection [IP: 00e1] ####
    #### System.Net.HttpWebRequest::SubmitRequest [IP: 0013] ####
    #### System.Net.HttpWebRequest::GetResponse [IP: 000c] ####
    #### N.Net.MailNotify+SendMesageRequest::Send [IP: 004d] ####

What can be done, so Cobra will work simultaneously ?

Regards,
Jack

_Dejan · March 23, 2012, 7:53am

Check this:
http://www.tinyclr.com/forum/23/6126/

Jack2 · March 23, 2012, 8:26am

But for me it is not a sollution.
I may check that dns is available, but another connection will hang.
Why is Cobra freezing on this request?

Jeff_Birt · March 23, 2012, 9:28am

My guess: because it is a blocking call. You could do this operation in a separate thread from your UI so the whole board is not setting waiting on the HttpWebRequest.

Jack2 · March 23, 2012, 10:51am

It is done in separate thread.
But all other threads are stopped.

Jeff_Birt · March 23, 2012, 11:43am

You mean you have no other threads running when you call the blocking method? Or, do you mean calling HTTPRequest stops all other threads? If so how do you know it stops all other threads?

Jack2 · March 23, 2012, 11:45am

I have very main function with blinking led:


public static void Main()
        {
            Led = new OutputPort((Cpu.Pin)FEZ_Pin.Digital.LED, false);

            Setup();

            while (true)
            {
                Thread.Sleep(500);
                Program.LED(true);
                Thread.Sleep(500);
                Program.LED(false);
            }
        }

When it is done LED stops blinking.

Jeff_Birt · March 23, 2012, 12:08pm

is your HttpRequest done by ‘SetUp();’? If so the LED will never start blinking until set up returns. Unless you create a new thread to run the Http code it in will run in the same thread as your Main.

Jack2 · March 23, 2012, 12:17pm

HttpWebRequest is done in seperate thread.

Loop of blinking LED is status that Cobra is working.

Jack2 · March 23, 2012, 1:03pm

Sample app demonstrating behaviour:


public class Program : Microsoft.SPOT.Application
    {
        public static void Main()
        {
            Thread thread = new Thread(new ThreadStart(Http));
            thread.Start();

            OutputPort Led = new OutputPort((Cpu.Pin)FEZ_Pin.Digital.LED, false);

            while (true)
            {

                Thread.Sleep(500);
                Debug.Print(DateTime.Now.ToUniversalTime() + ": Led: ON");
                Led.Write(true);
                Thread.Sleep(500);
                Debug.Print(DateTime.Now.ToUniversalTime() + ": Led: OFF");
                Led.Write(false);
            }
        }

        public static void Http()
        {
            Thread.Sleep(5000);
            try
            {
                Debug.Print(DateTime.Now.ToUniversalTime() + ": Request: START");
                HttpWebRequest request = (HttpWebRequest)HttpWebRequest.Create("http://www.google.pl");
                HttpWebResponse response = (HttpWebResponse)request.GetResponse();
            }
            catch (Exception)
            {
                Debug.Print(DateTime.Now.ToUniversalTime() + ": Request: EXCEPTION");
            }
        }

    }

Output:


01/01/2009 01:28:13: Led: ON
01/01/2009 01:28:14: Led: OFF
01/01/2009 01:28:14: Led: ON
01/01/2009 01:28:15: Led: OFF
01/01/2009 01:28:16: Led: ON
01/01/2009 01:28:16: Led: OFF
01/01/2009 01:28:17: Led: ON
01/01/2009 01:28:17: Led: OFF
01/01/2009 01:28:18: Led: ON
01/01/2009 01:28:18: Request: START
    #### Exception System.Net.Sockets.SocketException - CLR_E_FAIL (3) ####
    #### Message: 
    #### Microsoft.SPOT.Net.SocketNative::getaddrinfo [IP: 0000] ####
    #### System.Net.Dns::GetHostEntry [IP: 0008] ####
    #### System.Net.HttpWebRequest::EstablishConnection [IP: 00e1] ####
    #### System.Net.HttpWebRequest::SubmitRequest [IP: 0013] ####
    #### System.Net.HttpWebRequest::GetResponse [IP: 000c] ####
    #### InetTest.Program::Http [IP: 002f] ####
    #### SocketException ErrorCode = -1
    #### SocketException ErrorCode = -1
A first chance exception of type 'System.Net.Sockets.SocketException' occurred in Microsoft.SPOT.Net.dll
    #### SocketException ErrorCode = -1
    #### SocketException ErrorCode = -1
    #### Exception System.Net.WebException - 0x00000000 (3) ####
    #### Message: host not available
    #### System.Net.HttpWebRequest::EstablishConnection [IP: 00f1] ####
    #### System.Net.HttpWebRequest::SubmitRequest [IP: 0013] ####
    #### System.Net.HttpWebRequest::GetResponse [IP: 000c] ####
    #### InetTest.Program::Http [IP: 002f] ####
01/01/2009 01:28:52: Led: OFF
A first chance exception of type 'System.Net.WebException' occurred in System.Http.dll
    #### Exception System.Net.WebException - 0x00000000 (3) ####
    #### Message: 
    #### System.Net.HttpWebRequest::GetResponse [IP: 00d3] ####
    #### InetTest.Program::Http [IP: 002f] ####
A first chance exception of type 'System.Net.WebException' occurred in System.Http.dll
01/01/2009 01:28:53: Request: EXCEPTION
The thread '<No Name>' (0x3) has exited with code 0 (0x0).
01/01/2009 01:28:53: Led: ON
01/01/2009 01:28:53: Led: OFF
01/01/2009 01:28:54: Led: ON
01/01/2009 01:28:55: Led: OFF
01/01/2009 01:28:55: Led: ON
01/01/2009 01:28:56: Led: OFF
01/01/2009 01:28:56: Led: ON
01/01/2009 01:28:57: Led: OFF
01/01/2009 01:28:57: Led: ON
01/01/2009 01:28:58: Led: OFF
01/01/2009 01:28:58: Led: ON

As you can see after Request: START there is no blinking of LED for 35 seconds.

WouterH · March 23, 2012, 4:20pm

Can you comment out all Debug.Print calls and see what’s happening?

Jack2 · March 23, 2012, 4:34pm

The delay of not blinking LED is the same.

WouterH · March 23, 2012, 4:47pm

and what if you deploy a release version?

Jack2 · March 23, 2012, 4:52pm

Still the same.

WouterH · March 23, 2012, 4:58pm

Then I’m out of guesses. Seems like the DNS request blocks the whole thread sheduler…

godefroi · March 23, 2012, 8:27pm

NETMF doesn’t have preemptive multitasking, it’s cooperative. That means if something (in this case, the network stack) doesn’t release the CPU back to the framework, then nothing else gets done until it does.

I think.

Jack2 · March 25, 2012, 7:47am

Do You see any workaround for that?

It is really unacceptable that system will be freezed for 30 seconds.

Jack

Gus_Issa · March 25, 2012, 8:31am

I agree with you. I think you should post your code and output to Microsoft to comment. Keep us updated please.

www.netmf.com

godefroi · March 25, 2012, 9:34am

The simple fix is to reduce the timeout for sockets. Other than that, you’d need asynchronous I/O, which isn’t a minor feature.