Breaking Down a Simple Python App

Now for the client side:

   1 #!/usr/bin/env python
   2 # a simple TCP client
  
   3 from socket import *
   4 from time import time
   5 from time import sleep
   6 import sys
   7 BUFSIZE = 4096
  
   8 class CmdLine:
   9     def __init__(s,host):
  10         s.__HOST = host
  11         s.__PORT = 29876
  12         s.__ADDR = (s.__HOST,s.__PORT)
  13         s.__sock = None
  
  14     def makeConnection(s):
  15         s.__sock = socket( AF_INET,SOCK_STREAM)
  16         s.__sock.connect(s.__ADDR)
  
  17     def sendCmd(s, cmd):
  18         s.__sock.send(cmd)
  
  19     def getResults(s):
  20         data = s.__sock.recv(BUFSIZE)
  21         print data
   
  22 if __name__ == '__main__':
  23     conn = CmdLine('localhost')
  24     conn.makeConnection()
  25     conn.sendCmd('DUMMY CMD')
  26     conn.getResults()
  27     conn.sendCmd('BYE')

Line 15 creates a TCP socket, just like the server program. Line 16 creates a connection to the server. Remember, the server is "listening" for this connection. You must provide in HOST the IP address of the server or a resolvable host name. In this example we use "localhost" which will normally resolve to the loopback address. In line 18 we send a message to the server. In line 20 we receive a message from the server. That is it. That is all the communication necessary.

Of course this is a very simple example, which does not accomplish anything useful. But with some modification, these two classes can be used for your client server application. In a simple environment, the TCP stack would buffer enough packets so that the server could keep up with its job of listening.

In a more complicated environment, multiple threads might be required and possibly queues, however these are subjects for another article.

Breaking Down a Simple Python App
Breaking Down a Simple Python App