If you running Android X86 inside a virtual machine (such as VirtualBox) and would like to use it to debug your apps with ADB but still cannot connect you may find useful to do what follows:

Open the terminal inside your emulated device (alt+f1) and type:

setprop service.adb.tcp.port 5555
stop adbd
start adbd

then type:

netcfg

and note down the provided IP address.

then on your development machine type:

adb connect <ipaddress>:5555

Works wonders :)