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
and note down the provided IP address.
then on your development machine type:
adb connect <ipaddress>:5555