server.py
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#!/usr/bin/env python
###############################################################################
# mjc-broker #
# server.py #
# #
# (C) 2016 David Zhong #
# #
# Permission is hereby granted, free of charge, to any person obtaining a #
# copy of this software and associated documentation files (the "Software"), #
# to deal in the Software without restriction, including without limitation #
# the rights to use, copy, modify, merge, publish, distribute, sublicense, #
# and/or sell copies of the Software, and to permit persons to whom the #
# Software is furnished to do so, subject to the following conditions: #
# #
# The above copyright notice and this permission notice shall be included in #
# all copies or substantial portions of the Software. #
# #
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR #
# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, #
# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE #
# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER #
# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING #
# FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER #
# DEALINGS IN THE SOFTWARE. #
###############################################################################
import asyncore
import json
import random
import socket
import sys
usage = "usage: server.py <host> <port>"
VERSION_MAJOR = 0
VERSION_MINOR = 1
VERSION_REVISION = 0
class BrokerGeneralError(Exception): pass
class BrokerFatalError(Exception): pass
class BrokerHandler(asyncore.dispatcher_with_send):
def __init__(self, sock, database):
asyncore.dispatcher_with_send.__init__(self, sock)
self.database = database
self.name = None
self.buffer = ""
def send(self, data):
asyncore.dispatcher_with_send.send(self, json.dumps(data))
asyncore.dispatcher_with_send.send(self, "\r\n\r\n")
def handle_read(self):
self.buffer += self.recv(1024)
packets = self.buffer.split("\r\n\r\n")
self.buffer = packets[-1]
[self.ProcessPDU(x) for x in packets[:-1]]
def handle_close(self):
if self.name is not None:
self.database.RemoveClient(self.name)
self.close()
print "Closed connection from %s" % repr(self.addr)
def GetAddress(self):
return self.addr[0]
def ProcessPDU(self, packet):
try:
message = json.loads(packet)
except ValueError:
return
try:
typ = message["type"]
except KeyError:
self.SendFatalError("packet did not contain a message type")
return
if typ == "register":
action = self.ProcessRegister
elif typ == "pair":
action = self.ProcessPair
else:
self.SendFatalError("'%s' is not a valid message type" % typ)
return
try:
action(message)
except BrokerFatalError as e:
self.SendFatalError(e.message)
return
except BrokerGeneralError as e:
self.SendGeneralError(e.message)
return
def ProcessRegister(self, message):
try:
name = message["name"]
except KeyError:
raise BrokerFatalError("'register' packet must contain 'name'")
self.name = name
address = self.GetAddress()
self.database.AddClient(name, address, self)
self.SendRegisterOk()
def ProcessPair(self, message):
try:
respondent = message["respondent"]
except KeyError:
raise BrokerFatalError("'pair' packet must contain 'respondent'")
self.database.SendPairRequest(self.name, respondent)
def SendFatalError(self, message):
packet = {
"type": "fatal",
"message": message
}
self.send(packet)
print "Fatal error from %s: %s" % (self.GetAddress(), message)
self.handle_close()
def SendGeneralError(self, message):
packet = {
"type": "error",
"message": message
}
self.send(packet)
def SendPairing(self, name, local_port, remote_address, remote_port):
packet = {
"type": "pair",
"name": name,
"local_port": local_port,
"remote_address": remote_address,
"remote_port": remote_port
}
self.send(packet)
def SendClientList(self, names):
packet = {
"type": "clients",
"clients": names
}
self.send(packet)
def SendRegisterOk(self):
packet = {
"type": "registerok",
"name": self.name,
"address": self.GetAddress()
}
self.send(packet)
class BrokerDatabase(object):
def __init__(self):
self.clients = {}
def AddClient(self, name, address, handler):
if name in self.clients:
raise BrokerGeneralError("name already in use")
self.clients[name] = (address, handler)
self.RefreshClientList()
def RemoveClient(self, name):
if name in self.clients:
del self.clients[name]
self.RefreshClientList()
def SendPairRequest(self, proponent, respondent):
if proponent not in self.clients:
raise BrokerFatalError("user not registered")
if respondent not in self.clients:
raise BrokerGeneralError("requested user no longer available")
if respondent == proponent:
raise BrokerGeneralError("cannot pair with self")
r_address, r_handler = self.clients[respondent]
p_address, p_handler = self.clients[proponent]
p_port = r_port = random.randint(49200, 49300)
while r_port == p_port:
r_port = random.randint(49200, 49300)
r_handler.SendPairing(proponent, r_port, p_address, p_port)
p_handler.SendPairing(respondent, p_port, r_address, r_port)
def RefreshClientList(self):
client_names = self.clients.keys()
[handler.SendClientList(client_names) for address, handler in self.clients.values()]
class BrokerServer(asyncore.dispatcher, BrokerDatabase):
def __init__(self, host, port):
asyncore.dispatcher.__init__(self)
BrokerDatabase.__init__(self)
self.create_socket(socket.AF_INET, socket.SOCK_STREAM)
self.set_reuse_addr()
self.bind((host, port))
self.listen(5)
print "Listening on %s:%d" % (host, port)
def handle_accept(self):
pair = self.accept()
if pair is not None:
sock, addr = pair
print "New connection from %s" % repr(addr)
handler = BrokerHandler(sock, self)
def main():
if len(sys.argv) < 3:
print usage
return
HOST = sys.argv[1]
try:
PORT = int(sys.argv[2])
except ValueError:
print "invalid port"
print usage
return
server = BrokerServer(HOST, PORT)
asyncore.loop()
if __name__ == "__main__":
main()