Can't send from Viewer to Host using Virtual Channels with Windows Desktop Sharing/RDPCOMAPILib

Question

I'm creating a windows desktop sharing app and have everything working except the virtual channels for sending chat messages. I can send messages from the host to the Viewer but not vice versa. The Viewer is using the ActiveX RDPViewer. The problem is I can't get the OnChannelDataRecieved event to fire on the host. I know some people have had trouble with this before but any help would be appreciated.

Here is some snippets that might help. Viewer

RDPCOMAPILib.IRDPSRAPIVirtualChannel chan;
chan = rdpViewer.VirtualChannelManager.CreateVirtualChannel(name, RDPCOMAPILib.CHANNEL_PRIORITY.CHANNEL_PRIORITY_HI, 0);

Then when sending i call

chan.SendData(message, (int)RDPCOMAPILib.RDPENCOMAPI_CONSTANTS.CONST_ATTENDEE_ID_HOST, 0);

Host

chan = rdp.VirtualChannelManager.CreateVirtualChannel(name, RDPCOMAPILib.CHANNEL_PRIORITY.CHANNEL_PRIORITY_HI, 0);
foreach(IRDPSRAPIAttendee attendee in rdp.Attendees)
            this.vc.SetAccess(attendee.Id, RDPCOMAPILib.CHANNEL_ACCESS_ENUM.CHANNEL_ACCESS_ENUM_SENDRECEIVE);

Then I call this to send data

chan.SendData(message, (int)RDPCOMAPILib.RDPENCOMAPI_CONSTANTS.CONST_ATTENDEE_ID_EVERYONE, 0);

Answer 1

Using RDPENCOMAPI_CONSTANTS.CONST_ATTENDEE_ID_EVERYONE didn't work for me. The only way I solved that issue was to use SendData iterating over session's attendees.

foreach (IRDPSRAPIAttendee a in _ctx.activeSession.Attendees)
    virtualChannel.SendData(msg, a.Id, Convert.ToUInt32(CHANNEL_FLAGS.CHANNEL_FLAGS_LEGACY));

While this solves the Host-to-Viewer communication I still can't receive any message from a connected viewer, registed on the same virtual channel and using RDPENCOMAPI_CONSTANTS.CONST_ATTENDEE_ID_HOST constant.

What I've done server-side is to create a new RDPSession and a virtual channel

activeSession = new RDPSession();
virtualChannel = activeSession.VirtualChannelManager.CreateVirtualChannel("myproto", CHANNEL_PRIORITY.CHANNEL_PRIORITY_HI, (uint)CHANNEL_FLAGS.CHANNEL_FLAGS_LEGACY);

create a new handler for OnChannelDataReceived event and start the RDP session.

activeSession.OnChannelDataReceived += new _IRDPSessionEvents_OnChannelDataReceivedEventHandler(OnChannelDataReceived);
activeSession.Open();

Event handler looks like this:

    private void OnChannelDataReceived(object pChannel, int lAttendeeId, string bstrData) {
       switch(bstrData) 
       {
            /* Handle commands here */
            case "mycmd":
                /* Process command and reply using SendData */
                break;

       }
    }

Viewer runs on Windows 10 while server runs on Windows 7 and they both uses RDPCOMAPI generated from Windows 7 rdpcomen.dll using tlbimp.exe tool.

Answer 2

Here's the technique that I use that works well for my needs:

//----------------------------------------------------------------------------------------
// On the server/host, create a new session
//----------------------------------------------------------------------------------------
RDPSession session = new RDPSession();

// Then create a virtual channel
IRDPSRAPIVirtualChannel virtualChannel1 = session.VirtualChannelManager.CreateVirtualChannel("foo", CHANNEL_PRIORITY.CHANNEL_PRIORITY_HI, (uint)CHANNEL_FLAGS.CHANNEL_FLAGS_LEGACY);

// Now open the session
session.Open()

// And connect to the received event
session.OnChannelDataReceived += new _IRDPSessionEvents_OnChannelDataReceivedEventHandler(OnChannelDataReceived);

private void OnChannelDataReceived(object pChannel, int lAttendeeId, string bstrData) {
    Debug.WriteLine("Server::OnChannelDataReceived" + bstrData.Trim());
}

//----------------------------------------------------------------------------------------
// On the Client/Viewer side.
//----------------------------------------------------------------------------------------

// AxRDPViewer is the RDPViewer control on your form. Connect using the appropriate criteria.
AxRDPViewer.Connect(strInvitation, strName, strPassword);

// "Bind" the virtual channel by creating one using the same name as the one created on
// the server side.
IRDPSRAPIVirtualChannel virtualChannel1 = RDPViewer.VirtualChannelManager.CreateVirtualChannel("foo", CHANNEL_PRIORITY.CHANNEL_PRIORITY_HI, (uint)CHANNEL_FLAGS.CHANNEL_FLAGS_LEGACY);

// Hook the data received event
RDPViewer.OnChannelDataReceived += new AxRDPCOMAPILib._IRDPSessionEvents_OnChannelDataReceivedEventHandler(RDPViewer_OnChannelDataReceived);

private void RDPViewer_OnChannelDataReceived(object sender, AxRDPCOMAPILib._IRDPSessionEvents_OnChannelDataReceivedEvent e) {
    Debug.WriteLine("Client::OnChannelDataReceived:" + e.bstrData.Trim());
}

//----------------------------------------------------------------------------------------
// Sending data
//----------------------------------------------------------------------------------------

// Now, on both the server and client side, you can send data like this:

virtualChannel1.SendData("yippie!", (int)RDPENCOMAPI_CONSTANTS.CONST_ATTENDEE_ID_EVERYONE, (uint)CHANNEL_FLAGS.CHANNEL_FLAGS_LEGACY);

I hope that helps. I actually struggled with this for awhile, only to end up realizing that I was launching a modal dialog over my form that was responsible for hooking the session events. So don't do that. ;)