Enable Steam, but disable Steam network sessions

Hi.
I have server and client, everything is good: server opens port 7777, client connects with console command “open ip:port?key1=value1”.
But now i need use Steam (to get SteamID64). I linked Steam: server uses “create session”, opens 27015, 27036 ports, 7777 is closed. Client uses “find/join session”. Using variables is not available in connection URL.

Is it possible to leave first scheme, but take SteamID64 on client? All i need is take SteamID64 on client side and transfer it with client build’s version to server. Steam is not required on server side. Also i dont need any “sessions”.
Thank you.