Chat server & client using select.select (Python recipe) by Anand

ActiveState Code (http://code.activestate.com/recipes/531824/)

# First the server

#!/usr/bin/env python
#!/usr/bin/env python

"""
A basic, multiclient 'chat server' using Python's select module
with interrupt handling.

Entering any line of input at the terminal will exit the server.
"""

import select
import socket
import sys
import signal
from communication import send, receive

BUFSIZ = 1024


class ChatServer(object):
    """ Simple chat server using select """
    
    def __init__(self, port=3490, backlog=5):
        self.clients = 0
        # Client map
        self.clientmap = {}
        # Output socket list
        self.outputs = []
        self.server = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
        self.server.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
        self.server.bind(('',port))
        print 'Listening to port',port,'...'
        self.server.listen(backlog)
        # Trap keyboard interrupts
        signal.signal(signal.SIGINT, self.sighandler)
        
    def sighandler(self, signum, frame):
        # Close the server
        print 'Shutting down server...'
        # Close existing client sockets
        for o in self.outputs:
            o.close()
            
        self.server.close()

    def getname(self, client):

        # Return the printable name of the
        # client, given its socket...
        info = self.clientmap[client]
        host, name = info[0][0], info[1]
        return '@'.join((name, host))
        
    def serve(self):
        
        inputs = [self.server,sys.stdin]
        self.outputs = []

        running = 1

        while running:

            try:
                inputready,outputready,exceptready = select.select(inputs, self.outputs, [])
            except select.error, e:
                break
            except socket.error, e:
                break

            for s in inputready:

                if s == self.server:
                    # handle the server socket
                    client, address = self.server.accept()
                    print 'chatserver: got connection %d from %s' % (client.fileno(), address)
                    # Read the login name
                    cname = receive(client).split('NAME: ')[1]
                    
                    # Compute client name and send back
                    self.clients += 1
                    send(client, 'CLIENT: ' + str(address[0]))
                    inputs.append(client)

                    self.clientmap[client] = (address, cname)
                    # Send joining information to other clients
                    msg = '\n(Connected: New client (%d) from %s)' % (self.clients, self.getname(client))
                    for o in self.outputs:
                        # o.send(msg)
                        send(o, msg)
                    
                    self.outputs.append(client)

                elif s == sys.stdin:
                    # handle standard input
                    junk = sys.stdin.readline()
                    running = 0
                else:
                    # handle all other sockets
                    try:
                        # data = s.recv(BUFSIZ)
                        data = receive(s)
                        if data:
                            # Send as new client's message...
                            msg = '\n#[' + self.getname(s) + ']>> ' + data
                            # Send data to all except ourselves
                            for o in self.outputs:
                                if o != s:
                                    # o.send(msg)
                                    send(o, msg)
                        else:
                            print 'chatserver: %d hung up' % s.fileno()
                            self.clients -= 1
                            s.close()
                            inputs.remove(s)
                            self.outputs.remove(s)

                            # Send client leaving information to others
                            msg = '\n(Hung up: Client from %s)' % self.getname(s)
                            for o in self.outputs:
                                # o.send(msg)
                                send(o, msg)
                                
                    except socket.error, e:
                        # Remove
                        inputs.remove(s)
                        self.outputs.remove(s)
                        


        self.server.close()

if __name__ == "__main__":
    ChatServer().serve()

#############################################################################
# The chat client
#############################################################################
#! /usr/bin/env python

"""
Simple chat client for the chat server. Defines
a simple protocol to be used with chatserver.

"""

import socket
import sys
import select
from communication import send, receive

BUFSIZ = 1024

class ChatClient(object):
    """ A simple command line chat client using select """

    def __init__(self, name, host='127.0.0.1', port=3490):
        self.name = name
        # Quit flag
        self.flag = False
        self.port = int(port)
        self.host = host
        # Initial prompt
        self.prompt='[' + '@'.join((name, socket.gethostname().split('.')[0])) + ']> '
        # Connect to server at port
        try:
            self.sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
            self.sock.connect((host, self.port))
            print 'Connected to chat server@%d' % self.port
            # Send my name...
            send(self.sock,'NAME: ' + self.name) 
            data = receive(self.sock)
            # Contains client address, set it
            addr = data.split('CLIENT: ')[1]
            self.prompt = '[' + '@'.join((self.name, addr)) + ']> '
        except socket.error, e:
            print 'Could not connect to chat server @%d' % self.port
            sys.exit(1)

    def cmdloop(self):

        while not self.flag:
            try:
                sys.stdout.write(self.prompt)
                sys.stdout.flush()

                # Wait for input from stdin & socket
                inputready, outputready,exceptrdy = select.select([0, self.sock], [],[])
                
                for i in inputready:
                    if i == 0:
                        data = sys.stdin.readline().strip()
                        if data: send(self.sock, data)
                    elif i == self.sock:
                        data = receive(self.sock)
                        if not data:
                            print 'Shutting down.'
                            self.flag = True
                            break
                        else:
                            sys.stdout.write(data + '\n')
                            sys.stdout.flush()
                            
            except KeyboardInterrupt:
                print 'Interrupted.'
                self.sock.close()
                break
            
            
if __name__ == "__main__":
    import sys

    if len(sys.argv)<3:
        sys.exit('Usage: %s chatid host portno' % sys.argv[0])
        
    client = ChatClient(sys.argv[1],sys.argv[2], int(sys.argv[3]))
    client.cmdloop()

###############################################################################
# The communication module (communication.py)
###############################################################################
import cPickle
import socket
import struct

marshall = cPickle.dumps
unmarshall = cPickle.loads

def send(channel, *args):
    buf = marshall(args)
    value = socket.htonl(len(buf))
    size = struct.pack("L",value)
    channel.send(size)
    channel.send(buf)

def receive(channel):

    size = struct.calcsize("L")
    size = channel.recv(size)
    try:
        size = socket.ntohl(struct.unpack("L", size)[0])
    except struct.error, e:
        return ''
    
    buf = ""

    while len(buf) < size:
        buf = channel.recv(size - len(buf))

    return unmarshall(buf)[0]