Dies ist ein einfaches Socket-Programm, das einen Server und einige Clients hat. Clients senden ihre Texte verschlüsselt mit einer einfachen RSA-Kryptografie, dann entschlüsselt die Serverseite den Satz und sendet den entschlüsselten Satz zurück an den Client.

Server:

import socket
import sys
from thread import *
from math import *
from random import *
import random
HOST = ''   
PORT = 8888
size=2**16
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
print 'Socket created'

#Bind socket to local host and port
try:
    s.bind((HOST, PORT))
except socket.error , msg:
    print 'Bind failed. Error Code : ' + str(msg[0]) + ' Message ' + msg[1]
    sys.exit()

print 'Socket bind complete'

#Start listening on socket
s.listen(10)
print 'Socket now listening'

def decoder(codedString,d,n):
    breakcoded=[]
    coded=(codedString)
    #print coded;
    for i in range (len(coded)):
            breakcoded.append(chr(((int(coded[i])**d) % n)+48))
    stri= ""
    for i in range (len(breakcoded)):
            stri+=breakcoded[i]
    return stri

#Function for handling connections. This will be used to create threads
def clientthread(conn):
    #Sending message to connected client
    conn.send('Welcome to the server. Type something and hit enter\n') #send only takes string
    #infinite loop so that function do not terminate and thread do not end.
    while True:    
    #Receiving from client
        data = conn.recv(1024)
##        data=s.recv(size)
    l = int (data)
    #print l
    coded=[]
    i=0
    data1=conn.recv(size)
print 'Recieved n: ',data1
n = int (data1)
data2=conn.recv(size)
print 'Recieved d: ',data2
d = int (data2)
for i in range (l):
            data3=conn.recv(size)
            #print 'Recieved: ',data3
            print
            coded.append(data3)       
    print 'coded string has been recieved....'
    print ('coded string: ' , coded)
d= decoder(coded,d,n)
print d        
    reply = 'OK... your message decrypted as: ' + d
    if not d:
        break
    conn.sendall(reply)
#came out of loop
conn.close()
#now keep talking with the client
while 1:
    #wait to accept a connection - blocking call
    conn, addr = s.accept()
    print 'Connected with ' + addr[0] + ':' + str(addr[1])

    #start new thread takes 1st argument as a function name to be run, second is the tuple of     arguments to the function.
    start_new_thread(clientthread ,(conn,))

s.close()

Klient:

import socket
from math import *
from random import *
host='localhost'
port=8888
size=2**16
def declare():
        a = sample([5,3],2)
        return (a[0],a[1])
def coder(input_message):
        (p,q)=declare()
        for i in range (1):
                p=2**p-1
        for i in range (1):
                q=2**q-1
        #print p
        #print q
        #print ("n= ",p*q)
        #print a
        def gcd(a,b):
                if a%b==0:
                    return b
                elif a%b > 0:
                    s=a%b
                        return gcd(b,s)
                else:
                    raise ValueError
        n=p*q
        phi=(p-1)*(q-1)
        e=2
        while gcd(phi,e)!=1:
                e+=1
        d=1
        while ((e*d)%phi)!=1:
                d+=1
        public_key=(n,e)
        special_key=(n,d)
        ListOfAsciis=[]
        coded=[]
        breakcoded=[]
        for i in input_message:
                ListOfAsciis.append(ord(i)-48)
        for j in ListOfAsciis:
                coded.append((j**e)%n)
        #print ("e= ",e)
        #print ("d= ",d)
        #print ("coded= ",coded)
        for i in coded:
                breakcoded.append(chr(((i**d) % n)+48))
        #print ('n= ' , n)
        #print str(coded)
        #print coded
        return (d,n,str(coded[0]))
def decoder(codedString,d,n):
        #input_d= input("please enter your private key d: ")
        #input_n= input("please enter your private key n: ")
        #d = int (input_d)
        #n = int (input_n)
        breakcoded=[]
        coded=(codedString)
        print coded;
        for i in range (len(coded)):
                breakcoded.append(chr(((int(coded[i])**d) % n)+48))

        stri= ""
        for i in range (len(breakcoded)):
                stri+=breakcoded[i]
        return stri
s=socket.socket(socket.AF_INET,socket.SOCK_STREAM)
print 'socket created'
s.connect((host,port))
print 'connected'
data=s.recv(size)
print 'Recieved: ', data
while True:
    input_message= raw_input("please enter your message: ")
    message = list(input_message)
    s.send(str(len(message)))
##  (p,q)=declare()
    #n=p*q
    (d,n,c)=coder('i')

    n=str(n)
print "                  ",
print "                  ",
print "                  ",
print "                  ",
s.send(n)
print "                                                            ",
d=str(d)
s.send((d))
print "   ",
print "   ",
print "   ",
for i in range (len(message)):
            (d,n,c)=coder(input_message[i])
            print "                                                           ",
            print "   ",
            print "   ",
            s.send((c))
    print 'coded string has been sent to the server....'
    data=s.recv(size)
    print 'Recieved: ', data

jetzt ist das problem, dass das programm manchmal richtig funktioniert und manchmal nicht! in falschen fällen bekommt der server zwei send Items vom client von einem recv. was sollte ich