This is what happens: Click 'Join Server' ➨ Connecting ➨ Syncing cloud data ➨ Initializing ➨ **BF3 launches in the background** ➨ Logging in ➨ Connecting ➨ Loading level ➨ **BF3 is closed in the background** ➨ Game disconnected: could not join server.

Ezzel a módszerrel sikerült megoldani!

Smart Port Forwarding Installer

Program letölt, telepít.. majd
jobb egérgomb - add new forwarding port
TCP és UDP-vel is végre kell hajtani!
ezt az értéket kell belőni: 3659

így néz ki!

ECN Packets has been enabled by a Net Speed Tool

To fix this :
1. open a CMD prompt AS ADMINISTRATOR
2. type "netsh"
3. type "int tcp set global ecncapability=disabled"

ECN packets are Refused by EA. These are FAKE packets to fool the connection.

Most Common Causes
Broken UPNP on your router. Disable it.