L4D2不能联机

苏家小楼

前一阵子还能联机的，后来不知道怎么回事就不能联了。
单独自己建房间没有问题。
朋友开主机进去就是黑屏。

控制台那边显示如下：


Can't use cheat cvar fog_color in multiplayer, unless the server has sv_cheats set to 1.
Can't use cheat cvar fog_colorskybox in multiplayer, unless the server has sv_cheats set to 1.
Can't use cheat cvar fog_color in multiplayer, unless the server has sv_cheats set to 1.
Can't use cheat cvar fog_colorskybox in multiplayer, unless the server has sv_cheats set to 1.
Can't use cheat cvar fog_color in multiplayer, unless the server has sv_cheats set to 1.
Can't use cheat cvar fog_colorskybox in multiplayer, unless the server has sv_cheats set to 1.
Can't use cheat cvar r_farz in multiplayer, unless the server has sv_cheats set to 1.
Can't use cheat cvar r_farz in multiplayer, unless the server has sv_cheats set to 1.
Connecting to public(192.168.101.20:27015)
Sending UDP connect to public IP 192.168.101.20:27015
Server using '<none>' lobbies, requiring pw no, lobby id 0
RememberIPAddressForLobby: lobby 0 from address 192.168.101.20:27015
CSteam3Client::InitiateConnection: 192.168.101.20:27015
Connected to 192.168.101.20:27015

Left 4 Dead 2
Map: c2m1_highway
Players: 2 (0 bots) / 4 humans
Build: 4710
Server Number: 1

CAsyncWavDataCache:  3 .wavs total 0 bytes, 0.00 % of capacity
Error! Variable "$blendframes" is multiply defined in material "particle/smoke1/smoke1_add_nearcull"!
Downloading materials/models/infected/hunter/em3200_00_BM.vmt.
CBaseClientState::FileDenied: materials/models/infected/hunter/em3200_00_BM.vmt.



请问，是丢失了什么么？
求助，有什么办法么？