Question

For our current project we are using DBus (1.6.n).
It is largely accessed from C++ in shared memory mode, and this works really well.

I am now trying to access the same DBus from a C# program.

In order to try things out first, I downloaded the latest version of dbus-sharp I could find, and started the daemon included in the download to see if I could connect to it from my test C# app.

Whenever I make a connection, the daemon console shows that I am communicating with it, but as soon as I try to access any methods on the connection I get the error;

‘Access is denied: DBus.BusObject’

Here is the code I have tried;

        DBus.Bus dBus = null;
        try
        {
            //input address comes from the UI and ends up as "tcp:host=localhost,port=12345";
            //dBus = new Bus(InputAddress.Text + inputAddressExtension.Text);
            //string s = dBus.GetId();
            //dBus.Close();

            //DBus.Bus bus = DBus.Bus.System;
            //DBus.Bus bus = Bus.Open(InputAddress.Text + inputAddressExtension.Text);
            //DBus.Bus bus = DBus.Bus.Session;
            //DBus.Bus bus = DBus.Bus.Starter;

            var conn = Connection.Open(InputAddress.Text + inputAddressExtension.Text);
            var bus = conn.GetObject<Introspectable>(@"org.freedesktop.DBus.Introspectable", new ObjectPath("/org/freedesktop/DBus/Introspectable"));

            bus.Introspect();

        }
        finally
        {
            if(dBus != null)
                dBus.Close();
        }

The commented code produces the same error eventually too.

I have stepped through with the debugger and it always gets to the following code in the TypeImplementer.cs;

public Type GetImplementation (Type declType)
{
Type retT;

        lock (getImplLock)
            if (map.TryGetValue (declType, out retT))
                return retT;

        string proxyName = declType.FullName + "Proxy";

        Type parentType;

        if (declType.IsInterface)
            parentType = typeof (BusObject);
        else
            parentType = declType;

        TypeBuilder typeB = modB.DefineType (proxyName, TypeAttributes.Class | TypeAttributes.Public, parentType);

        if (declType.IsInterface)
            Implement (typeB, declType);

        foreach (Type iface in declType.GetInterfaces ())
            Implement (typeB, iface);

        retT = typeB.CreateType (); <======== Fails here ==========

        lock (getImplLock)
            map[declType] = retT;

        return retT;
    }

I have not found any useful examples or documentation about accessing DBus from C#, and there seem to be few recent entries about this anywhere, so maybe no-one else is trying this.

I am running the daemon in the same folder as the test program.
As I am running on windows, the daemon is listening on the tcp setting;

string addr = “tcp:host=localhost,port=12345”;

Since this is the example included with the download, I thought it would be really simple to get it going, but alas no luck yet.

Has anyone else been here and know the next piece of the puzzle?

Any ideas would be appreciated.

Answer 1

Having received no comment or response, I will answer the question with the information I have found since asking it.

There appears to be no useful C# interface to DBus. (By useful, I mean one that works!)
The only information or examples I could find are not up to date and no effort appears to be being expended on providing a working interface.

I have decided to interface with DBus by using a C++ implementation written as a Windows service, and my C# program will send messages to DBus via the service. This seems to work ok, so satisfies the business need.

I am disappointed not to be able to get the C# to DBus working, but there are lots of service bus implementations that work on Windows, so in future I will look at implementing those instead of DBus.

If anyone does come up with a workable, documented solution to accessing DBus from C# on Windows, I would still be interested to see it.