Sayın Bakanımızın Bulut Bilişim Yorumu!
Ekim 31, 2011 § Yorum yok § Kalıcı bağlantı
Python ile asal keşfi
Ekim 26, 2011 § Yorum yok § Kalıcı bağlantı
Bu python scripti Project Euler ile uğraştığım zaman kullandığım bazı fonksiyonlar içermektedir.
Dosyayı yüklemek için tıklayınız
İçeriği:
"""
primes.py -- Oregon Curriculum Network (OCN)
Feb 1, 2001 changed global var primes to _primes, added relative primes test
Dec 17, 2000 appended probable prime generating methods, plus invmod
Dec 16, 2000 revised to use pow(), removed methods not in text, added sieve()
Dec 12, 2000 small improvements to erastosthenes()
Dec 10, 2000 added Euler test
Oct 3, 2000 modified fermat test
Jun 5, 2000 rewrite of erastosthenes method
May 19, 2000 added more documentation
May 18, 2000 substituted Euclid's algorithm for gcd
Apr 7, 2000 changed name of union function to 'cover' for consistency
Apr 6, 2000 added union, intersection -- changed code of lcm, gcd
Apr 5, 2000 added euler, base, expo functions (renamed old euler to phi)
Mar 31, 2000 added sieve, renaming/modifying divtrial
Mar 30, 2000 added LCM, GCD, euler, fermat
Mar 28, 2000 added lcm
Feb 18, 2000 improved efficiency of isprime(), made getfactors recursive
"""
import time, random, operator
_primes = [2] # global list of primes
def iseven(n):
"""Return true if n is even."""
return n%2==0
def isodd(n):
"""Return true if n is odd."""
return not iseven(n)
def get2max(maxnb):
"""Return list of primes up to maxnb."""
nbprimes = 0
if maxnb < 2: return []
# start with highest prime so far
i = _primes[-1]
# and add...
i = i + 1 + isodd(i)*1 # next odd number
if i <= maxnb: # if more prime checking needed...
while i<=maxnb:
if divtrial(i): _primes.append(i) # append to list if verdict true
i=i+2 # next odd number
nbprimes = len(_primes)
else:
for i in _primes: # return primes =< maxnb, even if more on file
if i<=maxnb: nbprimes = nbprimes + 1
else: break # quit testing once maxnb exceeded
return _primes[:nbprimes]
def get2nb(nbprimes):
"""Return list of primes with nbprimes members."""
if nbprimes>len(_primes):
# start with highest prime so far
i = _primes[-1]
# and add...
i = i + 1 + isodd(i)*1
while len(_primes)<nbprimes:
if divtrial(i): _primes.append(i)
i=i+2
return _primes[:nbprimes]
def isprime(n):
"""
Divide by primes until n proves composite or prime.
Brute force algorithm, will wimp out for humongous n
return 0 if n is divisible
return 1 if n is prime"""
nbprimes = 0
rtnval = 1
if n == 2: return 1
if n < 2 or iseven(n): return 0
maxnb = n ** 0.5 # 2nd root of n
# if n < largest prime on file, check for n in list
if n <= _primes[-1]: rtnval = (n in _primes)
# if primes up to root(n) on file, run divtrial (a prime test)
elif maxnb <= _primes[-1]: rtnval = divtrial(n)
else:
rtnval = divtrial(n) # check divisibility by primes so far
if rtnval==1: # now, if still tentatively prime...
# start with highest prime so far
i = _primes[-1]
# and add...
i = i + 1 + isodd(i)*1 # next odd number
while i <= maxnb:
if divtrial(i): # test of primehood
_primes.append(i) # append to list if prime
if not n%i: # if n divisible by latest prime
rtnval = 0 # then we're done
break
i=i+2 # next odd number
return rtnval
def iscomposite(n):
"""
Return true if n is composite.
Uses isprime"""
return not isprime(n)
def divtrial(n):
"""
Trial by division check whether a number is prime."""
verdict = 1 # default is "yes, add to list"
cutoff = n**0.5 # 2nd root of n
for i in _primes:
if not n%i: # if no remainder
verdict = 0 # then we _don't_ want to add
break
if i >= cutoff: # stop trying to divide by
break # lower primes when p**2 > n
return verdict
def erastosthenes(n):
"""
Suggestions from Ka-Ping Yee, John Posner and Tim Peters"""
sieve = [0, 0, 1] + [1, 0] * (n/2) # [0 0 1 1 0 1 0...]
prime = 3 # initial odd prime
while prime**2 <= n:
for i in range(prime**2, n+1, prime*2):
sieve[i] = 0 # step through sieve by prime*2
prime += 1 + sieve[prime+1:].index(1) # get next prime
# filter includes corresponding integers where sieve = 1
return filter(lambda i, sieve=sieve: sieve[i], range(n+1))
def sieve(n):
"""
In-place sieving of odd numbers, adapted from code
by Mike Fletcher
"""
candidates = range(3, n+1, 2) # start with odds
for p in candidates:
if p: # skip zeros
if p*p>n: break # done
for q in xrange(p*p, n+1, 2*p): # sieving
candidates[(q-3)/2] = 0
return [2] + filter(None, candidates) # [2] + remaining nonzeros
def base(n,b):
"""
Accepts n in base 10, returns list corresponding to n base b."""
output = []
while n>=1:
n,r = divmod(n,b) # returns quotient, remainder
output.append(r)
output.reverse()
return output
def fermat(n,b=2):
"""Test for primality based on Fermat's Little Theorem.
returns 0 (condition false) if n is composite, -1 if
base is not relatively prime
"""
if gcd(n,b)>1: return -1
else: return pow(b,n-1,n)==1
def jacobi(a,n):
"""Return jacobi number.
source: http://www.utm.edu/research/primes/glossary/JacobiSymbol.html"""
j = 1
while not a == 0:
while iseven(a):
a = a/2
if (n%8 == 3 or n%8 == 5): j = -j
x=a; a=n; n=x # exchange places
if (a%4 == 3 and n%4 == 3): j = -j
a = a%n
if n == 1: return j
else: return 0
def euler(n,b=2):
"""Euler probable prime if (b**(n-1)/2)%n = jacobi(a,n).
(stronger than simple fermat test)"""
term = pow(b,(n-1)/2.0,n)
jac = jacobi(b,n)
if jac == -1: return term == n-1
else: return term == jac
def getfactors(n):
"""Return list containing prime factors of a number."""
if isprime(n) or n==1: return [n]
else:
for i in _primes:
if not n%i: # if goes evenly
n = n/i
return [i] + getfactors(n)
def gcd(a,b):
"""Return greatest common divisor using Euclid's Algorithm."""
while b:
a, b = b, a % b
return a
def lcm(a,b):
"""
Return lowest common multiple."""
return (a*b)/gcd(a,b)
def GCD(terms):
"Return gcd of a list of numbers."
return reduce(lambda a,b: gcd(a,b), terms)
def LCM(terms):
"Return lcm of a list of numbers."
return reduce(lambda a,b: lcm(a,b), terms)
def phi(n):
"""Return number of integers < n relatively prime to n."""
product = n
used = []
for i in getfactors(n):
if i not in used: # use only unique prime factors
used.append(i)
product = product * (1 - 1.0/i)
return int(product)
def relprimes(n,b=1):
"""
List the remainders after dividing n by each
n-relative prime * some relative prime b
"""
relprimes = []
for i in range(1,n):
if gcd(i,n)==1: relprimes.append(i)
print " n-rp's: %s" % (relprimes)
relprimes = map(operator.mul,[b]*len(relprimes),relprimes)
newremainders = map(operator.mod,relprimes,[n]*len(relprimes))
print "b * n-rp's mod n: %s" % newremainders
def testeuler(a,n):
"""Test Euler's Theorem"""
a = long(a)
if gcd(a,n)>1:
print "(a,n) not relative primes"
else:
print "Result: %s" % pow(a,phi(n),n)
def goldbach(n):
"""Return pair of primes such that p1 + p2 = n."""
rtnval = []
_primes = get2max(n)
if isodd(n) and n >= 5:
rtnval = [3] # 3 is a term
n = n-3 # 3 + goldbach(lower even)
if n==2: rtnval.append(2) # catch 5
else:
if n<=3: rtnval = [0,0] # quit if n too small
for i in range(len(_primes)):
# quit if we've found the answer
if len(rtnval) >= 2: break
# work back from highest prime < n
testprime = _primes[-(i+1)]
for j in _primes:
# j works from start of list
if j + testprime == n:
rtnval.append(j)
rtnval.append(testprime) # answer!
break
if j + testprime > n:
break # ready for next testprime
return rtnval
"""
The functions below have to do with encryption, and RSA in
particular, which uses large probable _primes. More discussion
at the Oregon Curriculum Network website is at
http://www.inetarena.com/~pdx4d/ocn/clubhouse.html
"""
def bighex(n):
hexdigits = list('0123456789ABCDEF')
hexstring = random.choice(hexdigits[1:])
for i in range(n):
hexstring += random.choice(hexdigits)
return eval('0x'+hexstring+'L')
def bigdec(n):
decdigits = list('0123456789')
decstring = random.choice(decdigits[1:])
for i in range(n):
decstring += random.choice(decdigits)
return long(decstring)
def bigppr(digits=100):
"""
Randomly generate a probable prime with a given
number of decimal digits
"""
start = time.clock()
print "Working..."
candidate = bigdec(digits) # or use bighex
if candidate&1==0:
candidate += 1
prob = 0
while 1:
prob=pptest(candidate)
if prob>0: break
else: candidate += 2
print "Percent chance of being prime: %r" % (prob*100)
print "Elapsed time: %s seconds" % (time.clock()-start)
return candidate
def pptest(n):
"""
Simple implementation of Miller-Rabin test for
determining probable primehood.
"""
bases = [random.randrange(2,50000) for x in range(90)]
# if any of the primes is a factor, we're done
if n<=1: return 0
for b in bases:
if n%b==0: return 0
tests,s = 0L,0
m = n-1
# turning (n-1) into (2**s) * m
while not m&1: # while m is even
m >>= 1
s += 1
for b in bases:
tests += 1
isprob = algP(m,s,b,n)
if not isprob: break
if isprob: return (1-(1./(4**tests)))
else: return 0
def algP(m,s,b,n):
"""
based on Algorithm P in Donald Knuth's 'Art of
Computer Programming' v.2 pg. 395
"""
result = 0
y = pow(b,m,n)
for j in range(s):
if (y==1 and j==0) or (y==n-1):
result = 1
break
y = pow(y,2,n)
return result
def invmod(a,b):
"""
Return modular inverse using a version Euclid's Algorithm
Code by Andrew Kuchling in Python Journal:
http://www.pythonjournal.com/volume1/issue1/art-algorithms/
-- in turn also based on Knuth, vol 2.
"""
a1, a2, a3 = 1L,0L,a
b1, b2, b3 = 0L,1L,b
while b3 != 0:
# The following division will drop decimals.
q = a3 / b3
t = a1 - b1*q, a2 - b2*q, a3 - b3*q
a1, a2, a3 = b1, b2, b3
b1, b2, b3 = t
while a2<0: a2 = a2 + a
return a2
# code highlighted using py2html.py version 0.8
bc ile asalları bulmak
Ekim 26, 2011 § Yorum yok § Kalıcı bağlantı
İnternetten bulduğum bir fonksiyonlar kümesine primegen(m,n) fonksiyonunu ekledim.
Çalıştırmak için
bc primes-db_bc.txt primegen(2,10) 3 5 7 Bulunan asal sayısı:3
olarak dönmektedir.
Dosyayı yüklemek için tıklayınız..
Linuxde değişkenler
Ekim 26, 2011 § Yorum yok § Kalıcı bağlantı
lsof ile Açık Dosyaların Tesbiti
Ekim 26, 2011 § Yorum yok § Kalıcı bağlantı
İsmi k, bash, init ile başlayan proseslerin açtığı dosyalar:
lsof -c k lsof -c bash lsof -c init
pkrumins kullanıcının başlattığı veya apache prosesinin açtığı dosyalar
lsof -u pkrumins -c apache
pkrumins kullanıcının başlattığı ve apache prosesinin açtığı dosyalar
lsof -a -u pkrumins -c bash
root kullanıcısı tarafından açılmamış açık dosyalar
lsof -u ^root
30297 pidli proses tarafından açılmış dosyalar
lsof +p 30297
/tmp dizini ve altındaki dizinleri/dosyaları kullanan proseslerin açtığı dosyalar.
lsof +D /tmp
Bütün internet soketlerini ve 80. portu kullanan programları öğrenmek:
lsof -i lsof -i :80 lsof -i :smtp
Bütün internet ve Unix soketlerini listelemek
lsof -i -U
TCP ve UDP proseslerini listelemek
lsof -i tcp lsof -i udp lsof -i udp:53 lsof -i tcp:80
lsof komutunu her saniye çalıştırmak
lsof -r 1
www.akadia.com sunucunusa UPD ile 123 portu üzerinden bağlanan prosesler
lsof -iUDP@www.akadia.com:123
Lisp
Ekim 26, 2011 § Yorum yok § Kalıcı bağlantı
(loop for x from 1 to 3
do (loop for y from 11 to 12
do (print (+ x y)) ))
(defun factors (num)
"This function will find the factors of the argument num."
(let ((l '()))
(do ((current 1 (1+ current)))
((> current (/ num current)))
(if (= 0 (mod num current))
(if (= current (/ num current))
(setf l (append l (list current)))
(setf l (append l (list current (/ num current)))))))
(sort l #'< )))
(defun coprimesp (num1 num2)
"Returns t if numbers are coprimes, nil otherwise."
(let ((flag t))
(dolist (atom1 (rest (factors num1)))
(dolist (atom2 (rest (factors num2)))
(if (= atom1 atom2)
(setf flag nil))))
flag))
(defun find-primes (top)
"Finds primes starting at one and searching up to given number, top."
(let ((l '()))
(dotimes (x top)
(if (= 2 (length (factors x)))
(setf l (append l (list x)))))
l))
(defun prime-factors (num)
(let ( (f (factor num)) (l '()) )
(dolist (element f)
(if (primep element)
(setf l (append l (list element)))
(setf l (append l (prime-factors element)))))
l))
(defun prime-p (n)
(declare ((speed 3) (safety 0) (fixnum-safety 0))
(fixnum n))
(cond
((and (<= n 11) (member n '(2 3 5 7 11)) t)
((= (rem n 2) 0) nil)
((= (rem n 3) 0) nil)
((= (rem n 5) 0) nil)
((= (rem n 7) 0) nil)
(t
(loop for i fixnum from 11 to (isqrt n) by 2
(when (= (rem n i) 0) (return-from prime-p nil))
t)))
(defun sieve5 (n)
"Returns a list of all primes from 2 to n"
(declare (fixnum n) (optimize (speed 3) (safety 0)))
(let* ((a (make-array n :element-type 'bit :initial-element 0))
(result (list 2))
(root (isqrt n)))
(declare (fixnum root))
(do ((i 3 (the fixnum (+ i 2))))
((>= i n) (nreverse result))
(declare (fixnum i))
(progn (when (= (sbit a i) 0)
(push i result)
(if (<= i root)
(do* ((inc (+ i i))
(j (* i i) (the fixnum (+ j inc))))
((>= j n))
(declare (fixnum j inc))
(setf (sbit a j) 1))))))))
(defun divides? (a b)
(= (mod b a) 0))
(defun find-divisor (n test-divisor)
(cond ((> (* test-divisor test-divisor) n) n)
((divides? test-divisor n) test-divisor)
(t (find-divisor n (+ test-divisor 1))))))
(defun smallest-divisor (n)
(find-divisor n 2))
(defun prime? (n)
(= n (smallest-divisor n)))
=== Parametre olan Fonksiyon isimleri===
(defun sum (term a next b)
(if (> a b)
0
(+ (funcall term a) (sum term (funcall next a) next b))))
(defun sum-int (a b)
(defun myidentity (a) a)
(sum #'myidentity a #'1+ b))
veya
(defun sum-int (a b)
(sum (lambda(x) x) a #'1+ b))
(defun sum-sqr (a b)
(defun square (a) (* a a))
(sum #'square a #'1+ b))
(defun mysqrt(x) (fixed-point (lambda(y) (average (/ x y) y)) 1))
(defun sum-of-digits(n)
(if (= (abs n) 0) 0 (+ (mod (abs n) 10) (sum-of-digits (/ (- (abs n) (mod (abs n) 10)) 10)))))
(defun factorial(n) (if (= n 0) 1 (* n (factorial (- n 1)))))
(reduce '+ (find-primes 2000000))
md5sum
Ekim 25, 2011 § Yorum yok § Kalıcı bağlantı
md5sum x.iso >> md5sums.txt md5sum y.iso >> md5sums.txt cat md5sums.txt b42ae2a31fd39ebd59358cb7027f8304 x.iso b44d0e2abdd53b0bde6f624060eb07f0 y.iso
md5sum kontrolü yapmak
md5sum -c md5sum.txt x.iso: OK y.iso: OK
Recursive md5sum kontrolü yapmak
find ./backup -type f -print0 | xargs -0 md5sum > /checksums_backup.md5 cd /orjinal md5sum -c checksums_backup.md5
Process bar ile dosya kopyalamak
Ekim 25, 2011 § Yorum yok § Kalıcı bağlantı
$ rsync -r -v --progress -e ssh root@remote-server:~/pictures /home/user/
receiving file list ...
366 files to consider
pictures/IMG_1141.jpg
3849245 100% 32.30kB/s 0:01:56 (xfer#30, to-check=335/366)
pictures/IMG_1142.jpg
4400662 100% 32.21kB/s 0:02:13 (xfer#31, to-check=334/366)
pictures/IMG_1172.jpg
2457600 71% 32.49kB/s 0:00:29
netstat ile port analizi
Ekim 25, 2011 § 1 yorum § Kalıcı bağlantı
Bütün açık portları görmek (dinleyen ve veri gönderen)
# netstat -a | more Active Internet connections (servers and established) Proto Recv-Q Send-Q Local Address Foreign Address State tcp 0 0 localhost:30037 *:* LISTEN udp 0 0 *:bootpc *:* Active UNIX domain sockets (servers and established) Proto RefCnt Flags Type State I-Node Path unix 2 [ ACC ] STREAM LISTENING 6135 /tmp/.X11-unix/X0 unix 2 [ ACC ] STREAM LISTENING 5140 /var/run/acpid.socket TCP porları için # netstat -at Active Internet connections (servers and established) Proto Recv-Q Send-Q Local Address Foreign Address State tcp 0 0 localhost:30037 *:* LISTEN tcp 0 0 localhost:ipp *:* LISTEN tcp 0 0 *:smtp *:* LISTEN tcp6 0 0 localhost:ipp [::]:* LISTEN
UDP portları için
# netstat -au Active Internet connections (servers and established) Proto Recv-Q Send-Q Local Address Foreign Address State udp 0 0 *:bootpc *:* udp 0 0 *:49119 *:* udp 0 0 *:mdns *:*
Sadece dinleyen soketlerin tesbiti
# netstat -l Active Internet connections (only servers) Proto Recv-Q Send-Q Local Address Foreign Address State tcp 0 0 localhost:ipp *:* LISTEN tcp6 0 0 localhost:ipp [::]:* LISTEN udp 0 0 *:49119 *:*
Portların istatistiklerini görmek için
# netstat -s
Ip:
11150 total packets received
1 with invalid addresses
0 forwarded
0 incoming packets discarded
11149 incoming packets delivered
11635 requests sent out
Icmp:
0 ICMP messages received
0 input ICMP message failed.
Tcp:
582 active connections openings
2 failed connection attempts
25 connection resets received
Udp:
1183 packets received
4 packets to unknown port received.
.....
Portları kullanan programların PID bilgisi için
# netstat -pt Active Internet connections (w/o servers) Proto Recv-Q Send-Q Local Address Foreign Address State PID/Program name tcp 1 0 ramesh-laptop.loc:47212 192.168.185.75:www CLOSE_WAIT 2109/firefox tcp 0 0 ramesh-laptop.loc:52750 lax:www ESTABLISHED 2109/firefox
Verileri sayısal olarak görmek için
# netstat -an veya # netsat -a --numeric-ports # netsat -a --numeric-hosts # netsat -a --numeric-users
Sürekli olarak netstat verilerine bakmak için
# netstat -c Active Internet connections (w/o servers) Proto Recv-Q Send-Q Local Address Foreign Address State tcp 0 0 ramesh-laptop.loc:36130 101-101-181-225.ama:www ESTABLISHED tcp 1 1 ramesh-laptop.loc:52564 101.11.169.230:www CLOSING tcp 0 0 ramesh-laptop.loc:43758 server-101-101-43-2:www ESTABLISHED tcp 1 1 ramesh-laptop.loc:42367 101.101.34.101:www CLOSING ^C
Çekirdeğin routing verisini görmek için
# netstat -r Kernel IP routing table Destination Gateway Genmask Flags MSS Window irtt Iface 192.168.1.0 * 255.255.255.0 U 0 0 0 eth2 link-local * 255.255.0.0 U 0 0 0 eth2 default 192.168.1.1 0.0.0.0 UG 0 0 0 eth2
Bir programın kullandığı portu tesbit etmek
# netstat -ap | grep ssh (Not all processes could be identified, non-owned process info will not be shown, you would have to be root to see it all.) tcp 1 0 dev-db:ssh 101.174.100.22:39213 CLOSE_WAIT - tcp 1 0 dev-db:ssh 101.174.100.22:57643 CLOSE_WAIT -
Netcat Kullanımı
Ekim 25, 2011 § Yorum yok § Kalıcı bağlantı
Netcat network için isviçre çakısı gibidir.
Netcat temel olarak verilen porttan ilgili sunucuya bağlanır, input olarak verilen bilgiyi bu sunucuya gönderir, sunucunun cevabını ise ekrana (stdout’a) basar.
Örneğin google.com sunucusuna bağlanalim.
[xxx@xxxxx ~]$ nc www.google.com 80 HEAD / HTTP/1.0 [enter] HTTP/1.0 302 Found Cache-Control: private Content-Type: text/html; charset=UTF-8 Location: http://www.google.com.tr/?gfe_rd=cr&ei=Z-uCU8XoI4Pe8geRnoG4Aw Content-Length: 262 Date: Mon, 26 May 2014 07:21:11 GMT Server: GFE/2.0 Alternate-Protocol: 80:quic
Aynı işi aşağıdaki gibi de yapabiliriz.
[xxxx@xxxxxx ~]$ echo -e "HEAD / HTTP/1.0\n" | nc www.google.com 80 HTTP/1.0 302 Found Cache-Control: private Content-Type: text/html; charset=UTF-8 Location: http://www.google.com.tr/?gfe_rd=cr&ei=POuCU5_5I9Da8ge8_ICIDw Content-Length: 262 Date: Mon, 26 May 2014 07:20:28 GMT Server: GFE/2.0 Alternate-Protocol: 80:quic
Netcat’i dinleyici servis olarak çalıştırmak için “-l ” kullanılabilir.
Böylece çift yönlü olarak sunucunun ilgili portuna direct edilmiş bilgiler bağlanan sunucunun ekranına basılılır.
# IP adresi 10.10.10.10 olan bilgisayarda [xxxx@xxxxxx ~]# uptime| nc -l 6666 # şimdi başka bir bilgisayardan, 10.10.10.10 bilgisayarının 6666 portuna bağlanalim: [xxxx@xxxxxx ~]$ nc 10.10.10.10 6666 10:44:26 up 37 min, 4 users, load average: 0.00, 0.02, 0.07
Bunun güzel bir uygulaması olan chat server olarak netcat kullanmak için
# IP adresi 10.10.10.10 olan bilgisayarda $ nc -l -p 12345 veya $ nc -l 12345 # şimdi dinleyen 10.10.10.10 bilgisayarının 12345 portuna bağlanalim: $ nc 10.10.10.10 12345
İki bilgisayar arasında dosya göndermek
# Dinleyen sunucu -> bağlanan sunucu yönüde transfer # IP adresi 192.168.1.10 olan bilgisayarda $ cat file | nc -l -p 6666 # Başka bir bilgisayardan $ nc 192.168.1.10 6666 > file # Bağlanan sunucu -> Dinleyen sunucu yönüde transfer # 192.168.1.10 adresli bilgisayardan $ nc -l -p 6666 -q 10 >output.txt # Başka bir bilgisayardan $ cat input.txt| nc 192.168.1.10 6666 -q 10 ile 10 saniye sonra kapanması isteniyor.
A bilgisayarındaki /data dizinindeki dosyaları B bilgisayarına göndermek
# IP adresi 192.168.1.10 olan bilgisayarda $ tar -cf - /data | nc -l -p 6666 # 192.168.1.10 ipli bilgisayara bağlanalim $ nc 192.168.1.10 6666 | tar -xf -
# Diğer bilgisayardan 10.10.10.2 ipli bilgisayara erişip 12345 portundan veri gönderilip 12346 porundan veri alınabilir.
# 10.10.10.2 ipli bilgisayarda $ nc -l 12345 | nc www.linuxwiki.net 80 | nc -l 12346 # Başka bir bilgisayardan $ nc 10.10.10.2 12345 linux ^C $ nc 10.10.10.2 12346 <!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML 2.0//EN"> <html><head> <title>501 Method Not Implemented</title> </head><body> <h1>Method Not Implemented</h1> <p>GET to /default.shtml not supported.<br /> </p> <p>Additionally, a 404 Not Found error was encountered while trying to use an ErrorDocument to handle the request.</p> <hr> <address>Apache Server at just135.justhost.com Port 80</address> </body></html>
Netcat ile herhangi bir process sunucu görevi görebilir.
Bunu sağlamak için -e kullanmak yeterli
$ nc -l -p 12345 -e /bin/bash $ nc localhost 12345 ls -las total 4288 4 drwxr-xr-x 15 pkrumins users 4096 2009-02-17 07:47 . 4 drwxr-xr-x 4 pkrumins users 4096 2009-01-18 21:22 .. 8 -rw------- 1 pkrumins users 8192 2009-02-16 19:30 .bash_history 4 -rw-r--r-- 1 pkrumins users 220 2009-01-18 21:04 .bash_logout ...
Netcat ile ilgili portu dinleyen program hakkında bilgi edinebiliriz.
[XXXX@XXXX ~]$ nc -vvv localhost 22 Connection to localhost 22 port [tcp/ssh] succeeded! SSH-2.0-OpenSSH_5.3 Protocol mismatch.
Aynı mantıkla netcat port scanner olarak da kullanılabilir.
[XXXX@XXXX ~]$ nc -vvv -z targetip 1-65535
Not: Netcat için bazı paketlerde kısıtlamalar getirilmiştir.
Orjinal kaynaktan yüklemek için
* Microsoft
http://www.vulnwatch.org/netcat/nc111nt.zip
* Linux/Unix/BSD
http://www.vulnwatch.org/netcat/nc110.tgz
* GNU
http://netcat.sourceforge.net/