You need to write an IPv6 compliant server or client and wonder what could be the differences between an IPv6 compliant server or client and its IPv4 counterpart.
We use the same approach as writing an echo client/server using IPv6. The only major difference is how the socket is created using IPv6 information.
Listing 12a shows an IPv6 echo server, as follows:
#!/usr/bin/env python
# Python Network Programming Cookbook -- Chapter - 3
# This program is optimized for Python 2.7.
# It may run on any other version with/without modifications.
import argparse
import socket
import sys
HOST = 'localhost'
def echo_server(port, host=HOST):
"""Echo server using IPv6 """
for res in socket.getaddrinfo(host, port, socket.AF_UNSPEC, socket.SOCK_STREAM, 0, socket.AI_PASSIVE):
af, socktype, proto, canonname, sa = res
try:
sock = socket.socket(af, socktype, proto)
except socket.error, err:
print "Error: %s" %err
try:
sock.bind(sa)
sock.listen(1)
print "Server listening on %s:%s" %(host, port)
except socket.error, msg:
sock.close()
continue
break
sys.exit(1)
conn, addr = sock.accept()
print 'Connected to', addr
while True:
data = conn.recv(1024)
print "Received data from the client: [%s]" %data
if not data: break
conn.send(data)
print "Sent data echoed back to the client: [%s]" %data
conn.close()
if __name__ == '__main__':
parser = argparse.ArgumentParser(description='IPv6 Socket Server Example')
parser.add_argument('--port', action="store", dest="port", type=int, required=True)
given_args = parser.parse_args()
port = given_args.port
echo_server(port)Listing 12b shows an IPv6 echo client, as follows:
#!/usr/bin/env python
# Python Network Programming Cookbook -- Chapter - 3
# This program is optimized for Python 2.7.
# It may run on any other version with/without modifications.
import argparse
import socket
import sys
HOST = 'localhost'
BUFSIZE = 1024
def ipv6_echo_client(port, host=HOST):
for res in socket.getaddrinfo(host, port, socket.AF_UNSPEC, socket.SOCK_STREAM):
af, socktype, proto, canonname, sa = res
try:
sock = socket.socket(af, socktype, proto)
except socket.error, err:
print "Error:%s" %err
try:
sock.connect(sa)
except socket.error, msg:
sock.close()
continue
if sock is None:
print 'Failed to open socket!'
sys.exit(1)
msg = "Hello from ipv6 client"
print "Send data to server: %s" %msg
sock.send(msg)
while True:
data = sock.recv(BUFSIZE)
print 'Received from server', repr(data)
if not data:
break
sock.close()
if __name__ == '__main__':
parser = argparse.ArgumentParser(description='IPv6 socket client example')
parser.add_argument('--port', action="store", dest="port", type=int, required=True)
given_args = parser.parse_args()
port = given_args.port
ipv6_echo_client(port)The server output is as follows:
$ python 3_12a_ipv6_echo_server.py --port=8800 Server lisenting on localhost:8800 Connected to ('127.0.0.1', 35034) Received data from the client: [Hello from ipv6 client] Sent data echoed back to the client: [Hello from ipv6 client]
The client output is as follows:
$ python 3_12b_ipv6_echo_client.py --port=8800 Send data to server: Hello from ipv6 client Received from server 'Hello from ipv6 client'
The IPv6 echo server first determines its IPv6 information by calling socket.getaddrinfo(). Notice that we passed the AF_UNSPEC protocol for creating a TCP socket. The resulting information is a tuple of five values. We use three of them, address family, socket type, and protocol, to create a server socket. Then, this socket is bound with the socket address from the previous tuple. It then listens to the incoming connections and accepts them. After a connection is made, it receives data from the client and echoes it back.
On the client-side code, we create an IPv6-compliant client socket instance and send the data using the send() method of that instance. When the data is echoed back, the recv() method is used to get it back.