Haha, hope this can help somebody.
to telnet to e680i:
1. may be we should make sure our pc's IP is in 192.168.0.x
then:
[root@localhost sean]# ifconfig usb0 192.168.1.1 up
[root@localhost sean]# telnet 192.168.1.2
Successful

2. samba
very simple!
[root@localhost sean]# ifconfig usb0 192.168.1.1 netmask 255.255.255.0 mtu 900
open folder, press Ctrl+L
Input: smb ://192.168.1.2/system

Now, its OK!