hi, for some time I have a problem that prevents me from exchanging with a user I care about in particular. I press that before when I had the ADSL we exchanged files quietly. but since I switched to a connection with the mobile phone via usb tethering, it was no longer possible to exchange. in fact the message appears to both me and him "both users behind firewalls". i also tried to temporarily disable windows firewall and avira antivirus. but it didn't help. I ask someone more experienced than me how I could solve this annoying problem that has been tormenting me for years.
thanks to those who will help me.