Use adb through Ethernet:
Get board IP address:
busybox ifconfig
ADBD default use USB output. Change it to ethernet:
setprop service.adb.tcp.port 5555
stop adbd
start adbd
On host, restart ADB:
export ADBHOST=<board IP address>
adb kill-server
adb start-server
You can also connect host to target device by this commands:
adb connect xxx.xxx.xxx.xxx(IP address)
if you want to disconnect, use
adb disconnect
Then you can connect to other device through ethernet or usb cable.
Thank you for the information Bing and Ming!