problem of connection multiplayers

OK, thank you, I hope that I understood well!
Here are screenshots.
PC1 :
180209101806639707.jpg

PC2 :

180209102006140084.jpg
 
Great, magnificent, that worked, thank you so much... :);)
Now what is what I can play with another pc the house and on-line at the same time ?
 
While using LAN, you can play with any PC on your network. If you want to play with someone not on your network, you would need to switch back to WAN.

Glad it's working!
 
Ah, thus I cannot play at the same time with somebody on my local area network and somebody outside the local area network ?
 
Ah, thus I cannot play at the same time with somebody on my local area network and somebody outside the local area network ?

You are correct. The only way to do that, would be to use Hamachi. Method #2 of the tutorial covers how to set that up on each PC.