Unable to load DLL 'mqrt.dll'

I've developed a WCF Service which is hosted as a Windows Service and exposes a MSMQ endpoint.

I have the client app on SERVER1, and the MSMQ and WCF Service on SERVER2.

When the SERVER1/ClientApp attempts to push a message on to the SERVER2 MSMQ, I get the following errror:

    System.TypeInitializationException: The type initializer for 'System.ServiceModel.Channels.Msmq' threw an exception. ---> System.DllNotFoundException: Unable to load DLL 'mqrt.dll': The specified module could not be found. (Exception from HRESULT: 0x8007007E)
       at System.ServiceModel.Channels.UnsafeNativeMethods.MQGetPrivateComputerInformation(String computerName, IntPtr properties)
       at System.ServiceModel.Channels.MsmqQueue.GetMsmqInformation(Version& version, Boolean& activeDirectoryEnabled)
       at System.ServiceModel.Channels.Msmq..cctor()
       --- End of inner exception stack trace ---
       at System.ServiceModel.Channels.Msmq.EnterXPSendLock(Boolean& lockHeld, ProtectionLevel protectionLevel)
       at System.ServiceModel.Channels.MsmqOutputChannel.OnSend(Message message, TimeSpan timeout)
       at System.ServiceModel.Channels.OutputChannel.Send(Message message, TimeSpan timeout)
       at System.ServiceModel.Channels.ServiceChannel.Call(String action, Boolean oneway, ProxyOperationRuntime operation, Object[] ins, Object[] outs, TimeSpan timeout)
       at System.ServiceModel.Channels.ServiceChannelProxy.InvokeService(IMethodCallMessage methodCall, ProxyOperationRuntime operation)
       at System.ServiceModel.Channels.ServiceChannelProxy.Invoke(IMessage message)

Exception rethrown at [7]: 
   at System.Runtime.Remoting.Proxies.RealProxy.HandleReturnMessage(IMessage reqMsg, IMessage retMsg)
   at System.Runtime.Remoting.Proxies.RealProxy.PrivateInvoke(MessageData& msgData, Int32 type)
   at FacilityManager.Service.NotificationsProcessorServiceReference.INotificationsProcessor.SendNewReactiveTaskNotifications(NewReactiveTaskDataContract newReactiveTaskDataContract)

Both SERVER1 and SERVER2 are running Windows Server 2008 R2 Enterprise (6.1 SP1), and both have had MSMQ installed via the Add Features in Server Manager.

I understand that the DLL is missing (fairly obvious from the error!), but I've no idea what I should be installing to get the dll where it should be.

A search in Windows Explorer shows that the DLL is present in the following directories on both servers....

C:\Windows\System32
C:\Windows\SysWOW64
C:\Windows\winsxs\x86_microsoft-windows-msmq-runtime-core_31bf3856ad364e35_6.1.7601.17514_none_5768e2ad17453bd6
C:\Windows\winsxs\amd64_microsoft-windows-msmq-runtime-core_31bf3856ad364e35_6.1.7601.17514_none_b3877e30cfa2ad0c

Any help appreciated.

Solution

I'm none the wiser but things are working now.

After hours on SO and Google, I ended up just checking that MSMQ was installed on both Servers by writing a quick console application with the code grabbed from here...

https://stackoverflow.com/a/16104212/192999

I ran the console app on both Server1 and Server2 and both came back with a result of True to IsMsmqInstalled.

I then ran my application and the "Unable to load DLL 'mqrt.dll'" error was no longer being raised.

I don't know if the call to NativeMethods.LoadLibrary("Mqrt.dll"); registered the DLL or something, but it certainly fixed my problem.

I hope this helps someone in the future!