"wireless serial cable" with a 8266 module?

What modules should I use if I want to transfer serial data between two controllers. Using some AT commands to start is allright but after that the connection should act like a serial cable. Is this possible? In my opinion Web/HTML server and client is too much here.

What about software or AT commands in the 8266 modules. I really would like to program the controller and not the 8266 modules.

LMI1:
after that the connection should act like a serial cable. Is this possible? In my opinion Web/HTML server and client is too much here. ...........I really would like to program the controller and not the 8266 modules.

"Wireless serial" is a term used for bluetooth which, in the absence of better explanation, may be all you need.

Xbees ?

ieee488:
Serial to WiFi Adapter for connecting RS232 to networks

That is quite close. For paid job some of the devices they sell would be ideal. But here I don't need RS232 levels and some modules like 8266 are very cheap.

Have a look at a HC-12.

or if you want the cheaper version , a HC-11, but it has lower range.