Socket Programming in Python

References

• http://docs.python.org/lib/socket-objects.html
• http://docs.python.org/lib/socket-example.html
• http://www.amk.ca/python/howto/sockets/
• http://www.evolt.org/article/Socket_Programming_in_Python/17/60276/
• http://www.example-code.com/python/ssl_client.asp
• http://python.about.com/od/networkingwithpython/ss/beg_web_client_5.htm
• http://www.java2s.com/Code/Python/Network/Socket-Client.htm
• http://pleac.sourceforge.net/pleac_python/sockets.html
• http://www.xmlblaster.org/mhonarc-xmlBlaster-devel/msg01129.html
• http://www.codefetch.com/search?qy=socket&lang=python
• http://www.nightmare.com/pythonwin/async_sockets.html

Also:

• File:PyNet.pdf

SSL Info

• http://mail.python.org/pipermail/python-list/2003-September/226813.html

Examples

Client

#!/usr/bin/env python

import socket

# Create an INET, STREAMing socket

s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)

# Now connect to the web server on port 80 - the normal http port

s.connect(("www.performiq.com.au", 80))

Simple HTTP Server

#!/usr/bin/env python

import socket

# Create an INET, STREAMing socket

s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)

# Bind the socket to a public host ip, and a well-known port

serversocket.bind((socket.gethostname(), 80))

# Become a server socket

serversocket.listen(5)

while True:
   # Accept connections from outside
   
   (clientsocket, address) = serversocket.accept()

   # Now do something with the clientsocket -
   # say, pretend this is a threaded server

   ct = client_thread(clientsocket)

   ct.run()

Socket Comm Class

Fixed Length

class socket_comm:
   '''demonstration class only 
      - coded for clarity, not efficiency
'''
   MSGLEN = 64

   def __init__(self, sock=None):
     if sock is None:
        self.sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
   else:
      self.sock = sock

   def connect(host, port):
      self.sock.connect((host, port))

   def send(msg):
      totalsent = 0
      while totalsent < self.MSGLEN:
         sent = self.sock.send(msg[totalsent:])
         if sent == 0:
            raise RuntimeError, "Socket connection failed..."
         totalsent += sent

   def recv():
      msg = ''
      while len(msg) < self.MSGLEN:
         chunk = self.sock.recv(self.MSGLEN-len(msg))
         if chunk == '':
            raise RuntimeError, "Socket connection failed..."
         msg += chunk
         return msg

Matched Pair

Reader

# Echo server program
import socket

HOST = ''                 # Symbolic name meaning the local host
PORT = 11001              # Arbitrary non-privileged port

s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)

s.bind((HOST, PORT))
s.listen(1)

conn, addr = s.accept()

print 'Connected by', addr

while 1:
    data = conn.recv(1024)
    if not data: break
    conn.send(data)

conn.close()

Client

# Echo client program
import socket

HOST = 'xxx.com.au'    # The remote host
PORT = 11001          # The same port as used by the server

s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)

s.connect((HOST, PORT))
s.send('Hello, world')

data = s.recv(1024)

s.close()

print 'Received', repr(data)

Usin SSL

import socket

s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)

s.connect(('www.verisign.com', 443))

ssl_sock = socket.ssl(s)

print repr(ssl_sock.server())
print repr(ssl_sock.issuer())

# Set a simple HTTP request -- use httplib in actual code.

ssl_sock.write("""GET / HTTP/1.0\r
Host: www.verisign.com\r\n\r\n""")

# Read a chunk of data.  Will not necessarily
# read all the data returned by the server.

data = ssl_sock.read()

# Note that you need to close the underlying socket, not the SSL object.

del ssl_sock

s.close()

Some Utility Functions

Data Format

import socket

# Convert human readable form to 32 bit value

packed_ip = socket.inet_aton("192.160.0.1")
packed_ip = socket.inet_aton("www.oreilly.com")

# Convert 32 bit value to ip adress

ip_adress = socket.inet_ntoa(packed_ip)

# Create socket object

socketobj = socket(family, type)  # Example socket.AF_INT, socket.SOCK_STREAM
       
# Get socketname

socketobj.getsockname()  # Example, get port adress of client

Socket Server

Examples

# Create a Server, calling handler for every client
# You can test it with "telnet localhost 9999"

from SocketServer import TCPServer
from SocketServer import BaseRequestHandler

class LocalHandler(BaseRequestHandler):
    def handle(self):
        print "I got an request"
        
server = TCPServer(("127.0.0.1", 9999), LocalHandler)
server.serve_forever()

This is an extension of above example...

import time

from SocketServer import TCPServer
from SocketServer import BaseRequestHandler

class MyHandler(BaseRequestHandler):
    def handle(self):
        # self.request is the socket object
        print "%s I got an request from ip=%s port=%s" % (
            time.strftime("%Y-%m-%d %H:%M:%S"),
            self.client_address[0],
            self.client_address[1]
            )
        self.request.send("What is your name?\n")
        bufsize=1024
        response=self.request.recv(bufsize).strip() # or recv(bufsize, flags)
        data_to_send="Welcome %s!\n" % response
        self.request.send(data_to_send) # or send(data, flags)
        print "%s connection finnished" % self.client_address[0]
        
server = TCPServer(("127.0.0.1", 9999), MyHandler)

server.serve_forever()

# -----------------
# Using select

import select
import socket

in_list = []
in_list.append(mysocket)
in_list.append(myfile)
# ...

out_list = []
out_list.append(...)

except_list = []
except_list.append(...)

(in_, out_, exc_) = select.select(in_list, out_list, except_list, timeout)

for fd in in_:
    print "Can read", fd
for fd in out_:
    print "Can write", fd
for fd in exc_:
    print "Exception on", fd

# Missing: setting TCP_NODELAY