After clean install of Android Studio I always get the error
Error:java.util.concurrent.ExecutionException: java.lang.RuntimeException: No server t
In my case, I did not need to re-download the sdk. I closed Android Studio and ran the following command in the Terminal:
sudo chmod 777 -R ~/Desktop/AndroidStudio
...where, ~/Desktop/AndroidStudio was the folder structure after Root which I needed to mention in order to provide permission to read all the SDK packages and perform required operation as and when necessary by the Android Studio, because my Sdk folder was inside "~/Desktop/AndroidStudio".
I am running Android Studio 3.0.1 on Ubuntu 16.04 LTS. This worked for me perfectly :-)