Co-Op on LAN between 2 PCs with 1 Steam account?

[goatzilla]

I have 2 laptops, 2 keyboards, 2 mice, 1 copy of Portal 2 on 1 Steam account. Is there any way for me to play Co-Op mode with my son between the 2 machines?

[Perro Salvaje]

It is not possible to play simultaneously with the same account.

[goatzilla]

:( So I need to either play on the same screen as him, or literally create a new Steam account and buy a second copy of Portal 2?

[MaddDoktor [Linux]]

Yes. Because even if you create another account and family share, both players cannot play a shared game at the same time.

[Liddack]

Actually it is possible play coop on LAN with offline mode:
https://gaming.stackexchange.com/a/26884
https://www.reddit.com/r/Portal/comments/3m6en3/playing_coop_with_a_friend_using_only_one_copy_of/

[4cylinder]

I was able to do this with Portal 2 and Splinter Cell Chaos Theory so far.

Just have one PC go into "offline mode" for Steam.

Most games do have some kind of CD key check though, so these two examples are the exception rather than the rule.