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server.py
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server.py
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# in remove client
# in propose
# out update
# in get
from socketserver import UDPServer, DatagramRequestHandler
import struct
from io import BytesIO
import time
import socket
import json
COMMANDS = {b'a' : 'add_client',
b'r' : 'remove_client',
b'p' : 'propose_element',
b'u' : 'update_element',
b'g' : 'get_element',
b'i' : 'is_there_a_server',
b't' : 'there_is_a_server'}
for key, command_name in list(COMMANDS.items()):
COMMANDS[command_name] = key
SERVER_PORT = 6028
def number2bytes(number):
return struct.pack('>l', number)
LENGTH_OF_NUMBER = len(number2bytes(0))
def read_number(file):
return struct.unpack('>l', file.read(LENGTH_OF_NUMBER))[0]
class Server(UDPServer):
# max_packet_size according to
# http://stackoverflow.com/questions/1098897/what-is-the-largest-safe-udp-packet-size-on-the-internet
max_packet_size = 65507
information = {}
## allow_reuse_address = True
def __init__(self, server_address, RequestHandlerClass, address_family = socket.AF_INET):
self.address_family = address_family
UDPServer.__init__(self, server_address, RequestHandlerClass)
self.values = {}
self.clients = set()
def handle_timeout():
self.__handle_timeout()
self._has_pending_requests = False
self.__handle_timeout = self.handle_timeout
self.handle_timeout = handle_timeout
def handle_pending_requests(self):
self._has_pending_requests = True
while self._has_pending_requests:
self.handle_request()
def server_discovered(self, address, bytes):
pass
class CommandRequestHandler(DatagramRequestHandler):
def handle(self):
self.clients.add(self.client_address)
while True:
command = self.rfile.read(1)
if not command: break
if command not in COMMANDS: break
name = 'cmd_' + COMMANDS[command]
method = getattr(self, name)
method()
def write_command(self, name):
self.wfile.write(COMMANDS[name])
def write_number(self, number):
self.wfile.write(number2bytes(number))
def read_number(self):
return read_number(self.rfile)
def write_bytes(self, bytes):
self.wfile.write(bytes)
def read_bytes(self):
return self.rfile.read()
def reply(self):
self.socket.sendto(self.wfile.getvalue(), self.client_address)
self.wfile = BytesIO()
def finish(self):
pass
@property
def values(self):
return self.server.values
@property
def clients(self):
return self.server.clients
class ServerRequestHandler(CommandRequestHandler):
def cmd_propose_element(self):
"""propose an element"""
number = len(self.values)
element = self.read_bytes()
self.values[number] = element
self.write_update_command(number)
bytes = self.wfile.getvalue()
for client in self.clients:
self.socket.sendto(bytes, client)
def cmd_get_element(self):
"""reply with the right element"""
number = read_number(self.rfile)
if number not in self.values:
return
self.write_update_command(number)
self.reply()
def write_update_command(self, number):
value = self.values[number]
self.write_command('update_element')
self.write_number(number)
self.write_bytes(value)
def cmd_is_there_a_server(self):
self.write_command('there_is_a_server')
self.write_bytes(json.dumps(self.server.information).encode('UTF-8'))
self.reply()
class ClientRequestHandler(CommandRequestHandler):
def cmd_update_element(self):
"""update an element"""
number = self.read_number()
bytes = self.read_bytes()
self.server.values[number] = bytes
class DiscoveryRequestHandler(CommandRequestHandler):
def cmd_there_is_a_server(self):
string = self.read_bytes().decode('UTF-8')
if string:
information = json.loads(string)
else:
information = {}
self.server.server_discovered(self.client_address, information)
def create_server(HandlerClass = ServerRequestHandler,
ServerClass = Server, port=SERVER_PORT, start_thread = True):
import threading
server_address = ('', port)
server = ServerClass(server_address, ServerRequestHandler)
t = threading.Thread(target = server.serve_forever)
t.deamon = True
if start_thread:
t.start()
server.thread = t
return server
def main(HandlerClass = ServerRequestHandler,
ServerClass = Server, port=SERVER_PORT):
import sys
server_address = ('', port)
serverd = ServerClass(server_address, HandlerClass)
sa = serverd.socket.getsockname()
print("Serving on", sa[0], "port", sa[1], "...")
try:
serverd.serve_forever()
except KeyboardInterrupt:
print("\nKeyboard interrupt received, exiting.")
serverd.server_close()
sys.exit(0)
if __name__ == '__main__':
main()