Binary data transfer issue

[Jordan Apgar]

Hi all,

I'm trying to transfer a binary file over xmlrpclib.   My test file is
a .jpeg file.  I can transfer all the data over but when I go to open
the .jpeg I get "Error interpreting JPEG image file (Invalid JPEG file
structure: SOS before SOF)"

here's the code:

===========Various Shared Functions========
#EncodeAES takes a Cipher c and encrypts a String s
EncodeAES = lambda c, s: base64.b64encode(c.encrypt(pad(s)))

#DecodeAES takes a Cipher C and decrypts the cyphertext e
    #then removes the padding from the decrypted string
DecodeAES = lambda c, e:
c.decrypt(base64.b64decode(e)).rstrip(PADDING)


CIPHER = AES.new("KEY")


# method to change strings back into tuples
def stringToTuple(string):
    if string[0] + string[-1] == "()":
        items = string[1:-1]
        items = items.split(',')
        return items
    else:
        raise ValueError("Badly formatted string (missing brackets).")

======client=================
 def Download(self, FileName, Data_Size=1024):
        ErrorCount = 0
        Pkt_Num = -1
        OldPkt_Num = Pkt_Num
        localFile = open("files/"+FileName, "wb")
        print
        print "Requesting First Packet"
        packet = self.client.download(EncodeAES(CIPHER, str(Pkt_Num)))
        if packet[0] == "False":
            print packet[1]
            return False
        packet = stringToTuple(DecodeAES(CIPHER, packet))
        if int(packet[0]) == -3:
            print "Received Error Packet"
        else:
            print "Received Packet: ", int(packet[0])

        print "packet[1], ", packet[2:-1]

        Pkt_Num = int(packet[0])

        while Pkt_Num >= 0 and ErrorCount <= 10:
            if (OldPkt_Num +1) == Pkt_Num:
                OldPkt_Num = OldPkt_Num +1
                localFile.write(binascii.
                                a2b_base64(packet[1][2:-1]))
#<<<<!!!!!<<< writing to the file on the client
                ErrorCount == 0
            else:
                ErrorCount = ErrorCount +1
                Pkt_Num = OldPkt_Num

            print "Requesting Packet: ", Pkt_Num +1
            packet = self.client.download(EncodeAES(CIPHER,
str(Pkt_Num)))
            packet = stringToTuple(DecodeAES(CIPHER, packet))
            Pkt_Num = int(packet[0])
            if int(packet[0]) == -3:
                print "Received Error Packet"
            elif int(packet[0]) == -2:
                print "Received EOF"
            else:
                print "Received Packet: ", int(packet[0])

        localFile.close()

        if Pkt_Num == -2:
            print packet[1][2:-1]
            return True
        elif Pkt_Num == -3:
            os.remove("files/"+FileName)
            print packet[1][2:-1]
            return False
        else:
            os.remove("files/"+FileName)
            print "Unexpected Packet: File Transfer Stopped"
            return False


==========Server Method=============
    def download(self, Pkt_Num):

        Old_Pkt_Num = self.PKT
        DataRate = self.DATA
        Pkt_Num = int(DecodeAES(CIPHER,Pkt_Num))
        if Pkt_Num == -1 and Old_Pkt_Num == -1:
            Pkt_Num = 0
            try:
                f = open("files/"+self.usr_dict[client][FILENAME],
"rb")
            except IOError:
                return EncodeAES(CIPHER,
                                 str((-3, "File Could Not be
opened")))
             data = binascii.b2a_base64(f.read((Pkt_Num+1 *
DataRate)))     #<<<<<<!!!!!!!<<<<<<<< reading from file
            f.close()
            self.usr_dict[client][PKT] = Pkt_Num
            return EncodeAES(CIPHER,
                             str((Pkt_Num, data)))

        elif Pkt_Num == Old_Pkt_Num:
            if Pkt_Num * DataRate >=
os.path.getsize("files/"+self.usr_dict[client][FILENAME]):
                return EncodeAES(CIPHER,
                             str((-2, "File Transfer Complete")))
            try:
                f = open("files/"+self.usr_dict[client][FILENAME],
"rb")
            except IOError:
               return EncodeAES(CIPHER,
                             str((-3, "File Could Not be opened")))
            data = f.read((Pkt_Num+1 * DataRate))
            data = None
            data = binascii.b2a_base64(f.read(DataRate))
#<<<<<<<<!!!!!!!<<<<<<< reading from file
            f.close()
            self.usr_dict[client][PKT] = Pkt_Num +1

            return EncodeAES(CIPHER,
                            str((Pkt_Num+1, data)))

      else:

            return EncodeAES(CIPHER,
                             str((-3, "Incorrect Packet Requested")))



Thank you all for the help,  I know there are better ways and transfer
protocol modules to but I'd like to do this without them.

~Jordan