# Sun RPC version 2 -- RFC1057.

# XXX There should be separate exceptions for the various reasons why

# XXX an RPC can fail, rather than using RuntimeError for everything

# XXX Need to use class based exceptions rather than string exceptions

# XXX The UDP version of the protocol resends requests when it does

# XXX not receive a timely reply -- use only for idempotent calls!

# XXX There is no provision for call timeout on TCP connections

import xdr

import socket

import os

RPCVERSION = 2

CALL = 0

REPLY = 1

AUTH_NULL = 0

AUTH_UNIX = 1

AUTH_SHORT = 2

AUTH_DES = 3

MSG_ACCEPTED = 0

MSG_DENIED = 1

SUCCESS = 0 # RPC executed successfully

PROG_UNAVAIL = 1 # remote hasn't exported program

PROG_MISMATCH = 2 # remote can't support version #

PROC_UNAVAIL = 3 # program can't support procedure

GARBAGE_ARGS = 4 # procedure can't decode params

RPC_MISMATCH = 0 # RPC version number != 2

AUTH_ERROR = 1 # remote can't authenticate caller

AUTH_BADCRED = 1 # bad credentials (seal broken)

AUTH_REJECTEDCRED = 2 # client must begin new session

AUTH_BADVERF = 3 # bad verifier (seal broken)

AUTH_REJECTEDVERF = 4 # verifier expired or replayed

AUTH_TOOWEAK = 5 # rejected for security reasons

class Packer(xdr.Packer):

def pack_auth(self, auth):

flavor, stuff = auth

self.pack_enum(flavor)

self.pack_opaque(stuff)

def pack_auth_unix(self, stamp, machinename, uid, gid, gids):

self.pack_uint(stamp)

self.pack_string(machinename)

self.pack_uint(uid)

self.pack_uint(gid)

self.pack_uint(len(gids))

for i in gids:

self.pack_uint(i)

def pack_callheader(self, xid, prog, vers, proc, cred, verf):

self.pack_uint(xid)

self.pack_enum(CALL)

self.pack_uint(RPCVERSION)

self.pack_uint(prog)

self.pack_uint(vers)

self.pack_uint(proc)

self.pack_auth(cred)

self.pack_auth(verf)

# Caller must add procedure-specific part of call

def pack_replyheader(self, xid, verf):

self.pack_uint(xid)

self.pack_enum(REPLY)

self.pack_uint(MSG_ACCEPTED)

self.pack_auth(verf)

self.pack_enum(SUCCESS)

# Caller must add procedure-specific part of reply

# Exceptions

BadRPCFormat = 'rpc.BadRPCFormat'

BadRPCVersion = 'rpc.BadRPCVersion'

GarbageArgs = 'rpc.GarbageArgs'

class Unpacker(xdr.Unpacker):

def unpack_auth(self):

flavor = self.unpack_enum()

stuff = self.unpack_opaque()

return (flavor, stuff)

def unpack_callheader(self):

xid = self.unpack_uint()

temp = self.unpack_enum()

if temp != CALL:

raise BadRPCFormat('no CALL but %r' % (temp,))

temp = self.unpack_uint()

if temp != RPCVERSION:

raise BadRPCVersion('bad RPC version %r' % (temp,))

prog = self.unpack_uint()

vers = self.unpack_uint()

proc = self.unpack_uint()

cred = self.unpack_auth()

verf = self.unpack_auth()

return xid, prog, vers, proc, cred, verf

# Caller must add procedure-specific part of call

def unpack_replyheader(self):

xid = self.unpack_uint()

mtype = self.unpack_enum()

if mtype != REPLY:

raise RuntimeError('no REPLY but %r' % (mtype,))

stat = self.unpack_enum()

if stat == MSG_DENIED:

stat = self.unpack_enum()

if stat == RPC_MISMATCH:

low = self.unpack_uint()

high = self.unpack_uint()

raise RuntimeError('MSG_DENIED: RPC_MISMATCH: %r' % ((low, high),))

if stat == AUTH_ERROR:

stat = self.unpack_uint()

raise RuntimeError('MSG_DENIED: AUTH_ERROR: %r' % (stat,))

raise RuntimeError('MSG_DENIED: %r' % (stat,))

if stat != MSG_ACCEPTED:

raise RuntimeError('Neither MSG_DENIED nor MSG_ACCEPTED: %r' % (stat,))

verf = self.unpack_auth()

stat = self.unpack_enum()

if stat == PROG_UNAVAIL:

raise RuntimeError('call failed: PROG_UNAVAIL')

if stat == PROG_MISMATCH:

low = self.unpack_uint()

high = self.unpack_uint()

raise RuntimeError('call failed: PROG_MISMATCH: %r' % ((low, high),))

if stat == PROC_UNAVAIL:

raise RuntimeError('call failed: PROC_UNAVAIL')

if stat == GARBAGE_ARGS:

raise RuntimeError('call failed: GARBAGE_ARGS')

if stat != SUCCESS:

raise RuntimeError('call failed: %r' % (stat,))

return xid, verf

# Caller must get procedure-specific part of reply

# Subroutines to create opaque authentication objects

def make_auth_null():

return ''

def make_auth_unix(seed, host, uid, gid, groups):

p = Packer()

p.pack_auth_unix(seed, host, uid, gid, groups)

return p.get_buf()

def make_auth_unix_default():

try:

from os import getuid, getgid

uid = getuid()

gid = getgid()

except ImportError:

uid = gid = 0

import time

return make_auth_unix(int(time.time()-unix_epoch()), \

socket.gethostname(), uid, gid, [])

_unix_epoch = -1

def unix_epoch():

"""Very painful calculation of when the Unix Epoch is.

This is defined as the return value of time.time() on Jan 1st,

1970, 00:00:00 GMT.

On a Unix system, this should always return 0.0. On a Mac, the

calculations are needed -- and hard because of integer overflow

and other limitations.

"""

global _unix_epoch

if _unix_epoch >= 0: return _unix_epoch

import time

now = time.time()

localt = time.localtime(now) # (y, m, d, hh, mm, ss, ..., ..., ...)

gmt = time.gmtime(now)

offset = time.mktime(localt) - time.mktime(gmt)

y, m, d, hh, mm, ss = 1970, 1, 1, 0, 0, 0

offset, ss = divmod(ss + offset, 60)

offset, mm = divmod(mm + offset, 60)

offset, hh = divmod(hh + offset, 24)

d = d + offset

_unix_epoch = time.mktime((y, m, d, hh, mm, ss, 0, 0, 0))

print("Unix epoch:", time.ctime(_unix_epoch))

return _unix_epoch

# Common base class for clients

class Client:

def __init__(self, host, prog, vers, port):

self.host = host

self.prog = prog

self.vers = vers

self.port = port

self.makesocket() # Assigns to self.sock

self.bindsocket()

self.connsocket()

self.lastxid = 0 # XXX should be more random?

self.addpackers()

self.cred = None

self.verf = None

def close(self):

self.sock.close()

def makesocket(self):

# This MUST be overridden

raise RuntimeError('makesocket not defined')

def connsocket(self):

# Override this if you don't want/need a connection

self.sock.connect((self.host, self.port))

def bindsocket(self):

# Override this to bind to a different port (e.g. reserved)

self.sock.bind(('', 0))

def addpackers(self):

# Override this to use derived classes from Packer/Unpacker

self.packer = Packer()

self.unpacker = Unpacker('')

def make_call(self, proc, args, pack_func, unpack_func):

# Don't normally override this (but see Broadcast)

if pack_func is None and args is not None:

raise TypeError('non-null args with null pack_func')

self.start_call(proc)

if pack_func:

pack_func(args)

self.do_call()

if unpack_func:

result = unpack_func()

else:

result = None

self.unpacker.done()

return result

def start_call(self, proc):

# Don't override this

self.lastxid = xid = self.lastxid + 1

cred = self.mkcred()

verf = self.mkverf()

p = self.packer

p.reset()

p.pack_callheader(xid, self.prog, self.vers, proc, cred, verf)

def do_call(self):

# This MUST be overridden

raise RuntimeError('do_call not defined')

def mkcred(self):

# Override this to use more powerful credentials

if self.cred is None:

self.cred = (AUTH_NULL, make_auth_null())

return self.cred

def mkverf(self):

# Override this to use a more powerful verifier

if self.verf is None:

self.verf = (AUTH_NULL, make_auth_null())

return self.verf

def call_0(self): # Procedure 0 is always like this

return self.make_call(0, None, None, None)

# Record-Marking standard support

def sendfrag(sock, last, frag):

x = len(frag)

if last: x = x | 0x80000000

header = (chr(int(x>>24 & 0xff)) + chr(int(x>>16 & 0xff)) + \

chr(int(x>>8 & 0xff)) + chr(int(x & 0xff)))

sock.send(header + frag)

def sendrecord(sock, record):

sendfrag(sock, 1, record)

def recvfrag(sock):

header = sock.recv(4)

if len(header) < 4:

raise EOFError

x = int(ord(header[0]))<<24 | ord(header[1])<<16 | \

ord(header[2])<<8 | ord(header[3])

last = ((x & 0x80000000) != 0)

n = int(x & 0x7fffffff)

frag = ''

while n > 0:

buf = sock.recv(n)

if not buf: raise EOFError

n = n - len(buf)

frag = frag + buf

return last, frag

def recvrecord(sock):

record = ''

last = 0

while not last:

last, frag = recvfrag(sock)

record = record + frag

return record

# Try to bind to a reserved port (must be root)

last_resv_port_tried = None

def bindresvport(sock, host):

global last_resv_port_tried

FIRST, LAST = 600, 1024 # Range of ports to try

if last_resv_port_tried is None:

import os

last_resv_port_tried = FIRST + os.getpid() % (LAST-FIRST)

for i in range(last_resv_port_tried, LAST) + \

range(FIRST, last_resv_port_tried):

last_resv_port_tried = i

try:

sock.bind((host, i))

return last_resv_port_tried

except socket.error as e:

(errno, msg) = e

if errno != 114:

raise socket.error(errno, msg)

raise RuntimeError('can\'t assign reserved port')

# Client using TCP to a specific port

class RawTCPClient(Client):

def makesocket(self):

self.sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)

def do_call(self):

call = self.packer.get_buf()

sendrecord(self.sock, call)

reply = recvrecord(self.sock)

u = self.unpacker

u.reset(reply)

xid, verf = u.unpack_replyheader()

if xid != self.lastxid:

# Can't really happen since this is TCP...

raise RuntimeError('wrong xid in reply %r instead of %r' % (

xid, self.lastxid))

# Client using UDP to a specific port

class RawUDPClient(Client):

def makesocket(self):

self.sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)

def do_call(self):

call = self.packer.get_buf()

self.sock.send(call)

try:

from select import select

except ImportError:

print('WARNING: select not found, RPC may hang')

select = None

BUFSIZE = 8192 # Max UDP buffer size

timeout = 1

count = 5

while 1:

r, w, x = [self.sock], [], []

if select:

r, w, x = select(r, w, x, timeout)

if self.sock not in r:

count = count - 1

if count < 0: raise RuntimeError('timeout')

if timeout < 25: timeout = timeout *2

## print 'RESEND', timeout, count

self.sock.send(call)

continue

reply = self.sock.recv(BUFSIZE)

u = self.unpacker

u.reset(reply)

xid, verf = u.unpack_replyheader()

if xid != self.lastxid:

## print 'BAD xid'

continue

break

# Client using UDP broadcast to a specific port

class RawBroadcastUDPClient(RawUDPClient):

def __init__(self, bcastaddr, prog, vers, port):

RawUDPClient.__init__(self, bcastaddr, prog, vers, port)

self.reply_handler = None

self.timeout = 30

def connsocket(self):

# Don't connect -- use sendto

self.sock.setsockopt(socket.SOL_SOCKET, socket.SO_BROADCAST, 1)

def set_reply_handler(self, reply_handler):

self.reply_handler = reply_handler

def set_timeout(self, timeout):

self.timeout = timeout # Use None for infinite timeout

def make_call(self, proc, args, pack_func, unpack_func):

if pack_func is None and args is not None:

raise TypeError('non-null args with null pack_func')

self.start_call(proc)

if pack_func:

pack_func(args)

call = self.packer.get_buf()

self.sock.sendto(call, (self.host, self.port))

try:

from select import select

except ImportError:

print('WARNING: select not found, broadcast will hang')

select = None

BUFSIZE = 8192 # Max UDP buffer size (for reply)

replies = []

if unpack_func is None:

def dummy(): pass

unpack_func = dummy

while 1:

r, w, x = [self.sock], [], []

if select:

if self.timeout is None:

r, w, x = select(r, w, x)

else:

r, w, x = select(r, w, x, self.timeout)

if self.sock not in r:

break

reply, fromaddr = self.sock.recvfrom(BUFSIZE)

u = self.unpacker

u.reset(reply)

xid, verf = u.unpack_replyheader()

if xid != self.lastxid:

## print 'BAD xid'

continue

reply = unpack_func()

self.unpacker.done()

replies.append((reply, fromaddr))

if self.reply_handler:

self.reply_handler(reply, fromaddr)

return replies

# Port mapper interface

# Program number, version and (fixed!) port number

PMAP_PROG = 100000

PMAP_VERS = 2

PMAP_PORT = 111

# Procedure numbers

PMAPPROC_NULL = 0 # (void) -> void

PMAPPROC_SET = 1 # (mapping) -> bool

PMAPPROC_UNSET = 2 # (mapping) -> bool

PMAPPROC_GETPORT = 3 # (mapping) -> unsigned int

PMAPPROC_DUMP = 4 # (void) -> pmaplist

PMAPPROC_CALLIT = 5 # (call_args) -> call_result

# A mapping is (prog, vers, prot, port) and prot is one of:

IPPROTO_TCP = 6

IPPROTO_UDP = 17

# A pmaplist is a variable-length list of mappings, as follows:

# either (1, mapping, pmaplist) or (0).

# A call_args is (prog, vers, proc, args) where args is opaque;

# a call_result is (port, res) where res is opaque.

class PortMapperPacker(Packer):

def pack_mapping(self, mapping):

prog, vers, prot, port = mapping

self.pack_uint(prog)

self.pack_uint(vers)

self.pack_uint(prot)

self.pack_uint(port)

def pack_pmaplist(self, list):

self.pack_list(list, self.pack_mapping)

def pack_call_args(self, ca):

prog, vers, proc, args = ca

self.pack_uint(prog)

self.pack_uint(vers)

self.pack_uint(proc)

self.pack_opaque(args)

class PortMapperUnpacker(Unpacker):

def unpack_mapping(self):

prog = self.unpack_uint()

vers = self.unpack_uint()

prot = self.unpack_uint()

port = self.unpack_uint()

return prog, vers, prot, port

def unpack_pmaplist(self):

return self.unpack_list(self.unpack_mapping)

def unpack_call_result(self):

port = self.unpack_uint()

res = self.unpack_opaque()

return port, res

class PartialPortMapperClient:

def addpackers(self):

self.packer = PortMapperPacker()

self.unpacker = PortMapperUnpacker('')

def Set(self, mapping):

return self.make_call(PMAPPROC_SET, mapping, \

self.packer.pack_mapping, \

self.unpacker.unpack_uint)

def Unset(self, mapping):

return self.make_call(PMAPPROC_UNSET, mapping, \

self.packer.pack_mapping, \

self.unpacker.unpack_uint)

def Getport(self, mapping):

return self.make_call(PMAPPROC_GETPORT, mapping, \

self.packer.pack_mapping, \

self.unpacker.unpack_uint)

def Dump(self):

return self.make_call(PMAPPROC_DUMP, None, \

None, \

self.unpacker.unpack_pmaplist)

def Callit(self, ca):

return self.make_call(PMAPPROC_CALLIT, ca, \

self.packer.pack_call_args, \

self.unpacker.unpack_call_result)

class TCPPortMapperClient(PartialPortMapperClient, RawTCPClient):

def __init__(self, host):

RawTCPClient.__init__(self, \

host, PMAP_PROG, PMAP_VERS, PMAP_PORT)

class UDPPortMapperClient(PartialPortMapperClient, RawUDPClient):

def __init__(self, host):

RawUDPClient.__init__(self, \

host, PMAP_PROG, PMAP_VERS, PMAP_PORT)

class BroadcastUDPPortMapperClient(PartialPortMapperClient, \

RawBroadcastUDPClient):

def __init__(self, bcastaddr):

RawBroadcastUDPClient.__init__(self, \

bcastaddr, PMAP_PROG, PMAP_VERS, PMAP_PORT)

# Generic clients that find their server through the Port mapper

class TCPClient(RawTCPClient):

def __init__(self, host, prog, vers):

pmap = TCPPortMapperClient(host)

port = pmap.Getport((prog, vers, IPPROTO_TCP, 0))

pmap.close()

if port == 0:

raise RuntimeError('program not registered')

RawTCPClient.__init__(self, host, prog, vers, port)

class UDPClient(RawUDPClient):

def __init__(self, host, prog, vers):

pmap = UDPPortMapperClient(host)

port = pmap.Getport((prog, vers, IPPROTO_UDP, 0))

pmap.close()

if port == 0:

raise RuntimeError('program not registered')

RawUDPClient.__init__(self, host, prog, vers, port)

class BroadcastUDPClient(Client):

def __init__(self, bcastaddr, prog, vers):

self.pmap = BroadcastUDPPortMapperClient(bcastaddr)

self.pmap.set_reply_handler(self.my_reply_handler)

self.prog = prog

self.vers = vers

self.user_reply_handler = None

self.addpackers()

def close(self):

self.pmap.close()

def set_reply_handler(self, reply_handler):

self.user_reply_handler = reply_handler

def set_timeout(self, timeout):

self.pmap.set_timeout(timeout)

def my_reply_handler(self, reply, fromaddr):

port, res = reply

self.unpacker.reset(res)

result = self.unpack_func()

self.unpacker.done()

self.replies.append((result, fromaddr))

if self.user_reply_handler is not None:

self.user_reply_handler(result, fromaddr)

def make_call(self, proc, args, pack_func, unpack_func):

self.packer.reset()

if pack_func:

pack_func(args)

if unpack_func is None:

def dummy(): pass

self.unpack_func = dummy

else:

self.unpack_func = unpack_func

self.replies = []

packed_args = self.packer.get_buf()

dummy_replies = self.pmap.Callit( \

(self.prog, self.vers, proc, packed_args))

return self.replies

# Server classes

# These are not symmetric to the Client classes

# XXX No attempt is made to provide authorization hooks yet

class Server:

def __init__(self, host, prog, vers, port):

self.host = host # Should normally be '' for default interface

self.prog = prog

self.vers = vers

self.port = port # Should normally be 0 for random port

self.makesocket() # Assigns to self.sock and self.prot

self.bindsocket()

self.host, self.port = self.sock.getsockname()

self.addpackers()

def register(self):

mapping = self.prog, self.vers, self.prot, self.port

p = TCPPortMapperClient(self.host)

if not p.Set(mapping):

raise RuntimeError('register failed')

def unregister(self):

mapping = self.prog, self.vers, self.prot, self.port

p = TCPPortMapperClient(self.host)

if not p.Unset(mapping):

raise RuntimeError('unregister failed')

def handle(self, call):

# Don't use unpack_header but parse the header piecewise

# XXX I have no idea if I am using the right error responses!

self.unpacker.reset(call)

self.packer.reset()

xid = self.unpacker.unpack_uint()

self.packer.pack_uint(xid)

temp = self.unpacker.unpack_enum()

if temp != CALL:

return None # Not worthy of a reply

self.packer.pack_uint(REPLY)

temp = self.unpacker.unpack_uint()

if temp != RPCVERSION:

self.packer.pack_uint(MSG_DENIED)

self.packer.pack_uint(RPC_MISMATCH)

self.packer.pack_uint(RPCVERSION)

self.packer.pack_uint(RPCVERSION)

return self.packer.get_buf()

self.packer.pack_uint(MSG_ACCEPTED)

self.packer.pack_auth((AUTH_NULL, make_auth_null()))

prog = self.unpacker.unpack_uint()

if prog != self.prog:

self.packer.pack_uint(PROG_UNAVAIL)

return self.packer.get_buf()

vers = self.unpacker.unpack_uint()

if vers != self.vers:

self.packer.pack_uint(PROG_MISMATCH)

self.packer.pack_uint(self.vers)

self.packer.pack_uint(self.vers)

return self.packer.get_buf()

proc = self.unpacker.unpack_uint()

methname = 'handle_' + repr(proc)

try:

meth = getattr(self, methname)

except AttributeError:

self.packer.pack_uint(PROC_UNAVAIL)

return self.packer.get_buf()

cred = self.unpacker.unpack_auth()

verf = self.unpacker.unpack_auth()

try:

meth() # Unpack args, call turn_around(), pack reply

except (EOFError, GarbageArgs):

# Too few or too many arguments

self.packer.reset()

self.packer.pack_uint(xid)

self.packer.pack_uint(REPLY)

self.packer.pack_uint(MSG_ACCEPTED)

self.packer.pack_auth((AUTH_NULL, make_auth_null()))

self.packer.pack_uint(GARBAGE_ARGS)

return self.packer.get_buf()

def turn_around(self):

try:

self.unpacker.done()

except RuntimeError:

raise GarbageArgs

self.packer.pack_uint(SUCCESS)

def handle_0(self): # Handle NULL message

self.turn_around()

def makesocket(self):

# This MUST be overridden

raise RuntimeError('makesocket not defined')

def bindsocket(self):

# Override this to bind to a different port (e.g. reserved)

self.sock.bind((self.host, self.port))

def addpackers(self):

# Override this to use derived classes from Packer/Unpacker

self.packer = Packer()

self.unpacker = Unpacker('')

class TCPServer(Server):

def makesocket(self):

self.sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)

self.prot = IPPROTO_TCP

def loop(self):

self.sock.listen(0)

while 1:

self.session(self.sock.accept())

def session(self, connection):

sock, (host, port) = connection

while 1:

try:

call = recvrecord(sock)

except EOFError:

break

except socket.error as msg:

print('socket error:', msg)

break

reply = self.handle(call)

if reply is not None:

sendrecord(sock, reply)

def forkingloop(self):

# Like loop but uses forksession()

self.sock.listen(0)

while 1:

self.forksession(self.sock.accept())

def forksession(self, connection):

# Like session but forks off a subprocess

import os

# Wait for deceased children

try:

while 1:

pid, sts = os.waitpid(0, 1)

except os.error:

pass

pid = None

try:

pid = os.fork()

if pid: # Parent

connection[0].close()

return

# Child

self.session(connection)

finally:

# Make sure we don't fall through in the parent

if pid == 0:

os._exit(0)

class UDPServer(Server):

def makesocket(self):

self.sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)

self.prot = IPPROTO_UDP

def loop(self):

while 1:

self.session()

def session(self):

call, host_port = self.sock.recvfrom(8192)

reply = self.handle(call)

if reply is not None:

self.sock.sendto(reply, host_port)

# Simple test program -- dump local portmapper status

def test():

pmap = UDPPortMapperClient('')

list = pmap.Dump()

list.sort()

for prog, vers, prot, port in list:

print(prog, vers, end=' ')

if prot == IPPROTO_TCP: print('tcp', end=' ')

elif prot == IPPROTO_UDP: print('udp', end=' ')

else: print(prot, end=' ')

print(port)

# Test program for broadcast operation -- dump everybody's portmapper status

def testbcast():

import sys

if sys.argv[1:]:

bcastaddr = sys.argv[1]

else:

bcastaddr = '<broadcast>'

def rh(reply, fromaddr):

host, port = fromaddr

print(host + '\t' + repr(reply))

pmap = BroadcastUDPPortMapperClient(bcastaddr)

pmap.set_reply_handler(rh)

pmap.set_timeout(5)

replies = pmap.Getport((100002, 1, IPPROTO_UDP, 0))

# Test program for server, with corresponding client

# On machine A: python -c 'import rpc; rpc.testsvr()'

# On machine B: python -c 'import rpc; rpc.testclt()' A

# (A may be == B)

def testsvr():

# Simple test class -- proc 1 doubles its string argument as reply

class S(UDPServer):

def handle_1(self):

arg = self.unpacker.unpack_string()

self.turn_around()

print('RPC function 1 called, arg', repr(arg))

self.packer.pack_string(arg + arg)

#

s = S('', 0x20000000, 1, 0)

try:

s.unregister()

except RuntimeError as msg:

print('RuntimeError:', msg, '(ignored)')

s.register()

print('Service started...')

try:

s.loop()

finally:

s.unregister()

print('Service interrupted.')

def testclt():

import sys

if sys.argv[1:]: host = sys.argv[1]

else: host = ''

# Client for above server

class C(UDPClient):

def call_1(self, arg):

return self.make_call(1, arg, \

self.packer.pack_string, \

self.unpacker.unpack_string)

c = C(host, 0x20000000, 1)

print('making call...')

reply = c.call_1('hello, world, ')

print('call returned', repr(reply))