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common.py
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common.py
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"""Common modiefied from phase 2."""
import json
import socket
import struct
import hashlib
MAX_MESSAGE_SIZE = 8192
def send(sock, message):
"""Encode and send a message on an open socket."""
message = json.dumps(message).encode()
nlen = len(message)
if nlen >= MAX_MESSAGE_SIZE:
return {"error": "maxmimum message size exceeded"}
slen = struct.pack("!i", nlen)
if sock.sendall(slen) is not None:
return {"error", "incomplete message"}
if sock.sendall(message) is not None:
return {"error", "incompletely sent message"}
return {}
def receive(sock):
"""Expect a message on an open socket."""
nlen = sock.recv(4, socket.MSG_WAITALL)
if not nlen:
return {"error": "can't receive"}
slen = (struct.unpack("!i", nlen)[0])
if slen >= MAX_MESSAGE_SIZE:
return {"error": "maximum response size exceeded"}
response = sock.recv(slen, socket.MSG_WAITALL)
return json.loads(response.decode())
def send_receive_range(host, port_low, port_high, message):
"""Send an RPC and return the result."""
for port in range(port_low, port_high):
response = send_receive(host, port, message)
if "error" in response:
continue
else:
return response
else:
return {"error": "can't connect to %s" % host}
def send_receive(host, port, message):
"""Encapsulate the send/receive functionality of an RPC client.
Parameters
host, port - host and port to connect to
message - arbitrary Python object to be sent as message
Return value
Response received from server
In case of error, returns a dict containing an "error" key
"""
port = int(port)
sock = None
try:
sock = socket.create_connection((host, port), 5)
if not sock:
return {"error": "can't connect to %s:%s" % (host, port)}
send_result = send(sock, message)
if "error" in send_result:
return send_result
receive_result = receive(sock)
return receive_result
except ValueError as e:
return {"error": "json encoding error %s" % e}
except socket.error as e:
return {"error": "can't connect to %s:%s because %s" % (host, port, e)}
finally:
if sock is not None:
sock.close()
def listen(port, handler, timeout=None):
"""A simple RPC server.
Parameters
port - port number to listen on for all interfaces
handler - function to handle respones, documented below
timeout - if not None, after how many seconds to invoke timeout handler
Return value
in case of error, returns a dict with "error" key
otherwise, function does not return until timeout handler returns
"abort"
The handler function is invoked by the server in response
handler is passed a dict containing a "cmd" key indicating the event
the following are possible values of the "cmd" key:
init: the port has been bound, please perform server initializiation
timeout: timeout occurred
anything else: RPC command received
the return value of the handler function is sent as an RPC response
"""
bindsock = None
try:
bindsock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
bindsock.bind(('', port))
bindsock.listen(3)
if timeout:
bindsock.settimeout(timeout)
if "abort" in handler({"cmd": "init", "port": port}, None):
return {"error": "listen: abort in init"}
sock = None
addr = None
while True:
try:
sock, (addr, accepted_port) = bindsock.accept()
nlen = sock.recv(4, socket.MSG_WAITALL)
if not nlen:
print "listen: invalid length"
continue
slen = struct.unpack("!i", nlen)[0]
if slen >= MAX_MESSAGE_SIZE:
print "listen: invalid message size %s" % slen
continue
msg = sock.recv(slen, socket.MSG_WAITALL)
if not msg:
print "listen: receive failed"
continue
jsonmsg = json.loads(msg)
try:
response = handler(jsonmsg, addr)
if "abort" in response:
print "listen: abort"
return response
break
except Exception as e:
print "listen: handler error: %s" % e
continue
json_response = json.dumps(response)
slen = struct.pack("!i", len(json_response))
sock.sendall(slen)
sock.sendall(json_response)
except socket.timeout:
if "abort" in handler({"cmd": "timeout"}, None):
return {"error": "listen: abort in timeout"}
except ValueError as e:
print "listen: json encoding error %s" % e
except socket.error as e:
print "listen: socket error %s" % e
finally:
if sock is not None:
sock.close()
except socket.error as e:
return {"error": "can't bind %s" % e}
finally:
if bindsock is not None:
bindsock.close()
def hash_number(r):
"""Return hash of a number."""
hashed = hashlib.sha1(r)
return int(str(hashed.hexdigest()), 16)