DesktopAgent2

The Web keeps progressing and each day there are more things you can do from a browser.

However, sometimes you need to access things that are only on the machine where your browser is running. For example, opening local office apps or accessing local devices.

Some time ago I had provided a similar project called DesktopAgent. That project works fine but there were some lessons learned from it:

• That project was meant as a too general approach. That project had a concept of plugins for extending functionality and I think that is too complicated. So this project is provided more like a template that provides just the basics, and then you are free to adjust it to your needs.

I also switched for a more general communication approach.

• Web Request can be too slow and not that reliable

When I wrote the old desktop agent, IE6 was still around (it is still around I know but let's say its dead), and now all browsers support WebSockets. So I decided to switch for an implementation based on WebSockets.

Ok, all those learned lessons bring then DesktopAgent2.

Desktop Agent2 is a simple template to help you get started on creating your DesktopAgent. DesktopAgent2 targets .NET Framework 4.5, so it can be used even from Windows 7.

Building

To build the code just open DesktopAgent2.csproj in Visual Studio

Testing

If you just want to test DesktopAgent2 you can build it from source of download the binary from the Releases link.

First you need to run the Agent

Next open the `test.html' page.

When you press connect, the page will send a connection request to the agent. Once connected the agent will indicate that it has a new client

Now you can press the test buttons. For example press Start Word

The Agent will display the json message it received

{"action":"Word","command":"open"}

In general the Agent usage is pretty simple:

       // create a JSON
       var msg = {'action':'Excel','command':'open'};
       //Send the JSON message
       agent.Send(JSON.stringify(msg)).
       // react to the response
       then(function() {
            alert('excel was opened');
        });

On the Agent you just modify the code to insert your custom actions:

    private void ExecuteActions(IWebSocketConnection webSocket, string message)
        {
            Invoke(new Action(() => txtLog.AppendText(message)));

            try
            {
                var action = JObject.Parse(message);
                var command = action["action"].Value<string>();
                switch (command)
                {
                    //Add your actions in this switch
                    case "WSH":
                        this.RunWSH(webSocket, action);
                        break;
                    case "ExecProgram":
                        this.RunProgram(webSocket, action);
                        break;
                    case "Excel":
                        this.ExcelAction(webSocket, action);
                        break;
                    case "Word":
                        this.WordAction(webSocket, action);
                        break;
                }
            }
            catch
            {
                // Just ignore
            }
        }

Secure communication

Enabling secure connections requires two things: using the scheme wss instead of ws, and pointing to an x509 certificate containing public and private key

The changes in code are easy. Just two lines:

    var server = new WebSocketServer("wss://0.0.0.0:996");
    server.Certificate = new System.Security.Cryptography.X509Certificates.X509Certificate2(@"M:\Program Files\OpenSSL-Win64\bin\secondtest.pfx", "test");

To create a certificate you can follow this guide: statianzo/Fleck#214 (comment)