Port Forwarding Samba

SMB uses ports 445/tcp and/or 139/tcp (usually just one is enough, but sometimes it's better to forward both). Additionally, the Windows SMB client requires Ping (ICMP Echo) to be open.

Note, however, that many residential ISPs globally block WAN connections from/to these ports, due to the large amount of worms attacking unpatched SMB servers.

Also note that the Windows SMB client always uses the same ports. You can't forward 4451/tcp to computer A and 4452/tcp to computer B, because there's no way to specify the port when connecting.