Parallel Server in Python

Question

I want to implement a parallel server. The server should acceppt more than one client at the same time. So that the client can send messages to the server.

A serial server is working awesome. I can connect, write, close and can connect again, no problem. Now I want to implement threads. So like: For every new client, there have to be a new thread that handles a TCP socket with one client.

My code for the serial server:

    #!/usr/bin/python           # This is server.py file

import socket               # Import socket module
import time

while True:
   s = socket.socket()         # Create a socket object
   host = socket.gethostname() # Get local machine name
   port = 12345                # Reserve a port for your service.
   s.bind((host, port))        # Bind to the port

   s.listen(5)                 # Now wait for client connection.

   c, addr = s.accept()     # Establish connection with client.
   print 'Got connection from', addr
   c.send('Please wait...')
   time.sleep(2)
   c.send('Thank you for connecting with your admin. Please write now.')

   while True:
      msg = c.recv(1024)
      if not msg:
         s.close()
         break
      elif msg == "close1234567890":
         print ("Connection with %s was closed by the client." % (addr[0]))
      else:
         print "%s: %s" % (addr[0], msg)

My TRY for the parallel server:

import socket              
import time
import thread


s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
host = socket.gethostname()
s.bind((host, 50999))       
s.listen(5)                

def session(conn, addr):
   while True:
      print 'Got connection from', addr
      conn.send('Please wait...')
      time.sleep(2)
      conn.send('Thank you for connecting with your admin. Please write now.')

      while True:
         msg = conn.recv(1024)
         if not msg:
            s.close()
            break
         elif msg == "close1234567890":
            print ("Connection with %s was closed by the client." % (addr[0]))
         else:
            print "%s: %s" % (addr[0], msg)

while True:
    conn, addr = s.accept()
    try:
       thread.start_new_thread(session(conn, addr))
    finally:
       s.close()

Error: I start the server, no prob. Then I start the Client and everything is normal. I can write and the messages are printed out by the server. Then I start a second client, but in this windows nothing happens. No chance to write from the second client.

Sry, I am absolutely beginner with threads ;)

laike9m · Accepted Answer · 2014-04-10 10:51:16Z

1

This is because you s.close() the socket. Here's modified code:

def session(conn, addr):
    while True:
        print 'Got connection from', addr
        conn.send('Please wait...')
        time.sleep(2)
        conn.send('Thank you for connecting with your admin. Please write now.')

        while True:
            msg = conn.recv(1024)
            if not msg:
                conn.close()
                break
            elif msg == "close1234567890":
                print ("Connection with %s was closed by the client." % (addr[0]))
            else:
                print "%s: %s" % (addr[0], msg)

while True:
    conn, addr = s.accept()
    thread.start_new_thread(session(conn, addr))

s.close()

I've tested it and works well. BTW I change your:

host = socket.gethostname()
s.bind((host, 50999))

to s.bind(('localhost', 50999)). I'm not sure why you need your machine name, and the original code doesn't work at all——there's no point binding hostname to a socket.

answered Apr 10, 2014 at 10:51

laike9m

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1 Comment

fuuman Over a year ago

Sry, but it doesn't work for my client code. Maybe it's an error in the client. I did not think, that I have to update this code, too. But maybe...

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