Is there such a RTSP Ping?

Question

I am currently working on a WinForm app to stream videos from IP camera using the RTSP protocol in C#. Everything worked fine. Part of the requirement for the app includes a function to check whether the IP camera is online or not.

So I did a ping function using the System.Net.NetworkInformation.Ping class to ping the IP camera. Say if the RTSP url of the camera is as follows rtsp://[CAMERA IP]:554/Master0-RTSP/1.0, I would only need to extract the [CAMERA IP] part and use the Ping class to see if the camera is online or not by using its IP.

Initially, it works until an issue came, say if one to enter an IP which may not be the intended IP Camera (say an IP of a computer) the ping function would still work if the entered IP of the entered device is online.

I tried to search for something like a RTSP ping but could not find one. Was hoping for any advices or opinions on this matter. Any example in C# are greatly appreciated. Thank you for your kind attention.

Answer 1

OPTIONS can possibly work but the standard specifies the correct way is through using theGET_PARAMETER.

RFC2326 outlines that clearly

http://www.ietf.org/rfc/rfc2326.txt

10.8 GET_PARAMETER

The GET_PARAMETER request retrieves the value of a parameter of a presentation or stream specified in the URI. The content of the reply and response is left to the implementation. GET_PARAMETER with no entity body may be used to test client or server liveness ("ping").

While GET_PARAMETER may not be supported by the server there is no way to tell how that server will react to the OPTIONS request which does not even require a sessionID. Therefor it cannot be guaranteed it will keep your existing session alive.

This is clear from reading the same RFC about the OPTIONS request

10.1 OPTIONS

The behavior is equivalent to that described in [H9.2]. An OPTIONS request may be issued at any time, e.g., if the client is about to try a nonstandard request. It does not influence server state.

Example:

 C->S:  OPTIONS * RTSP/1.0
        CSeq: 1
        Require: implicit-play
        Proxy-Require: gzipped-messages

 S->C:  RTSP/1.0 200 OK
        CSeq: 1
        Public: DESCRIBE, SETUP, TEARDOWN, PLAY, PAUSE

Note that these are necessarily fictional features (one would hope that we would not purposefully overlook a truly useful feature just so that we could have a strong example in this section).

If GET_PARAMETER is not supported then you would issue a PLAY request with the SessionId of the session you want to keep alive.

This should work even if OPTIONS doesn't as PLAY honors the Session ID and if you are already playing there is no adverse effect.

For the C# RtspClient see my project @ https://net7mma.codeplex.com/

And the article on CodeProject @ http://www.codeproject.com/Articles/507218/Managed-Media-Aggregation-using-Rtsp-and-Rtp

Answer 2

You can use RTSPClientSharp and do something like this:

public static async Task TestRTSPConnection(string rtspAddress, string user, string password)
{
        var serverUri = new Uri(rtspAddress);
        var credentials = new NetworkCredential(user, password);

        var connectionParameters = new ConnectionParameters(serverUri, credentials);
        var cancellationTokenSource = new CancellationTokenSource();

        var connectTask = ConnectAsync(connectionParameters, cancellationTokenSource.Token);

        if (await Task.WhenAny(connectTask, Task.Delay(15000 /*timeout*/)) == connectTask)
        {
            if (!connectTask.Result)
            {
                logger.Warn("Connection refused - check username and password");
            }

            logger.Info("Connection test completed");
        }
        else 
        {
            logger.Warn("Connection timed out - check username and password");
        }
    }

    private static async Task<bool> ConnectAsync(ConnectionParameters connectionParameters, CancellationToken token)
    {
        try
        {
            using (var rtspClient = new RtspClient(connectionParameters))
            {
                rtspClient.FrameReceived +=
                    (sender, frame) => logger.Info($"New frame {frame.Timestamp}: {frame.GetType().Name}");

                while (true)
                {
                    logger.Info("Connecting...");

                    try
                    {
                        await rtspClient.ConnectAsync(token);
                    }
                    catch (OperationCanceledException)
                    {
                        logger.Info("Finishing test before connection could be established. Check credentials");
                        return false;
                    }
                    catch (RtspClientException e)
                    {
                        logger.Error($"{e.Message}: {e.InnerException?.Message}");
                        return false;
                    }

                    logger.Info("Connected - camera is online");
                    return true;
                }
            }
        }
        catch (OperationCanceledException)
        {
            return false;
        }
    }

It works for me pretty well if you just care about pinging and if the camera is online or not. Also timeout happens when credentials are incorrect. You get direct failure if port is not exposed or connection is refused.