How to get the nrf DK device to be available on the internet?

Question

I am testing nrf5 IoT tcp client example. (in 
rf5_iot\examples\iot	cp\client) 
 
 DK side: 
 
 IP:2004::213:ddff:fe4c:6032 
 run as client. 
 2.6lowpan border router (raspberry PI3) 
 interface bt0 eth0 
 bt0: 
 IP:2004::ba27:ebff:fe15:ae01 
 run as server, app source code: 
 import socket
 import struct
 
 SERVER_ADDR = '2004::ba27:ebff:fe15:ae01'
 SERVER_PORT = 9000
 sock = socket.socket(socket.AF_INET6, socket.SOCK_STREAM)
 server_addr = (SERVER_ADDR, SERVER_PORT, 0, 0)
 sock.bind(server_addr)
 sock.listen(1)
 client, addr = sock.accept()
 print 'Connected'
 while 1:
 recv_data = client.recv(128)
 recv_len = len(recv_data)
 if recv_len >= 8:
 rx_sequence_number = 0
 rx_sequence_number = struct.unpack("!I", recv_data[:4])[0]
 data = struct.pack("!i", (rx_sequence_number)
 print(data)
 data += 'Pong'
 client.send(data)
 sock.close()
 del sock
 
 Now, the client and server sides work well. 
 But how to communicate with nrf DK(client) by using eth0? 
 Further more, how to get the nrf DK device to be available on the internet? need to bridge bt0 and eth0 ? 
 thanks!