@IsmaelMiguel is there a reason you want to kill LXDE? Your first question should be "How do I launch LXDE when a VNC connection comes in?", not 'HOw do I kill LXDE after i disconnect"
(LXDE is also fairly light, so the logic/reasoning behind killing it at disconnect is fuzzy...)
@IsmaelMiguel you could maybe try and script it, every-minute cronjob that executes a script to check if there's a currently established connection to the VNC server
http://www.commitstrip.com/en/2015/09/10/top-online-n00b-mistake-sharing-fake-news/ CommitStrip - Blog relating the daily life of web agencies developers Online n00b mistake #1 – Sharing fake news CommitStrip 1441904611
The time I went, peoples talked about so many possible architectures for different kind of applications, different new frameworks. All sort of crazy things