Recently, they updated something in security, and a method for running client via left4dead2.exe (with arguments) in the same machine with a server is no more working.
Instead, here is a walkaround to run the app directly from steam.exe.
I'm attaching the full code of .bat script (to run server + join simultaneously):
Spoiler
PHP Code:
:: For CS:GO SET "appID=730" SET "GAME_ALIAS=csgo" SET "MAP_NAME=de_dust2"
:: set path to your dedicated server''s srcds.exe SET "SERVER_DIR=E:\server\csgo"
:: Example for L4D2 (remove :: prefixes) ::SET "appID=550" ::SET "GAME_ALIAS=left4dead2" ::SET "MAP_NAME=c1m1_hotel" ::SET "SERVER_DIR=V:\server\l4d2"
SET "IP=192.168.31.4" SET "PORT=27016"
:: Remove unnecessary optional arguments by your wish SET OPTIONAL_ARG= -insecure +sv_pure 0 +sv_consistency 0 -debug -condebug
:: set path to your steam.exe SET "STEAM_DIR=C:\Program Files (x86)\Steam"