OsmoBTS - OsmocomBB emulation project

Dear Osmcom, I am working on a project, where I am connecting OsmoBTS with OsmocomBB without hardware. I am trying to remove l1 on both sides and connect OsmoBTS with BB application via simple unix sockets. Based on the further recommendations, I am using osmobts-trx branch. Currently I am able to handle messages between BTS and TRX driver on clock and control ports, and on BB side I am in state that phone wants to connect into a cell (so its waiting for BCCH) . I am now trying to find a possible way how to handle messages on data port , between BTS – TRX ( TRX is removed, there is my application instead), and forward these messages to my customized BB l1 interface . The thing is that I need to send to BB phone (layer23) messages in structures from gsm_04_08.h (i.e. gsm48_system_information_type_3). I am not sure if I will be able to get needed from the messages coming on the data port 5702. I found, that PCU creates unix socket on “/tmp/pcu_bts” , but only in case sysmoBTS is in use (please correct me if I am wrong), so this will be not possible due compilation errors without HW. Here I found the gsm48_system_information_type_3 messages. So basically I need somehow to get this message structures on my custom l1 BB interface. Do you have any idea how to do this ? Any advice will be highly appreciated. Many thanks you for your attention :) Best regards, Dominik Tamaskovic.