Windows RDP and Remmina: “Unable to connect to RDP server”

If you’ve been using Remmina to RDP to a Windows machine for some time and then all of suddenly find yourself running into the error Unable to connect to RDP server <address>, take a minute to read my experience before you go through some possibly-unnecessary steps.

I occasionally reboot my modem and router, and after doing so tonight, I found I was unable to RDP into a machine running Windows 7 Ultimate on my LAN from Remmina. I immediately checked to see if I could RDP to a Windows Server machine on the same LAN from the same Remmina client and could. So, I ruled out Remmina being the problem – or so I thought.

My next check was at the network. I figured that maybe the machine was either not connected to the network or had been assigned a different IP. So I then connected a monitor the machine and checked via ipconfig to verify that the IP address was the same. I still decided to reboot my router again.

Next, I checked and rechecked the RDP settings on the Windows machine to ensure that RDP was enabled. Everything looked fine on that end, so I moved to the firewall settings. The firewall was set to allow access to RDP on the machine.

Next, I went to the net for support. I searched “unable to RDP into Windows” and naturally found lots of various explanations and solutions. Knowing that I have VirtualBox setup on the computer with network drivers installed, I decided to narrow my search to include that. That’s when I found explanations regarding issues caused by the Host-Only virtual network connection that Windows sees as an “unidentifiable” network connection type. Having had issues with this limiting my network access on a computer in the past due to Windows taking precautions in thinking it is connected to an insecure network, I jumped at several solutions that involved registry edits to tell Windows that the network connection was virtual and host-only – and that it terminated at the machine itself. Re-enabled the driver and found problem was not resolved.

I then decided to boot into Windows on my laptop and see if Windows’ own RDP client could connect to the machine. It did, but the connection seemed sluggish. I then became suspicious that either the network or the machine’s NIC were somehow at fault – which didn’t rule out in my mind that the connection on the machine created by VirtualBox could be to blame as well. I then went into the Network and Sharing settings on the machine and disabled the connection. Rebooted the machine and found myself facing the same problem.

Finally, I wisened up and searched for help: “unable to connecto to Windows RDP using Remmina” and found the solution to my problem. Again, there were several suggested solutions, but I did find the one that worked for me. One solution suggested changing the Advanced > Security value in the connection’s profile in Remmina to RDP. This not only didn’t fix my problem, but caused additional problems with connecting to the machine.

The solution, surprising enough, was as simple as removing an entry in a file. I simply opened .~./freerdp/known_hosts and removed the line that corresponded to the host. I restarted Remmina and tried to connect, getting prompted to accept the host’s key, and was happily connected. Was a little agitated that I spent so much time and work trying to resolve a problem that was so easily fixed, but happy to again have the ability to RDP into my machine.