Python implements methods of network port forwarding and redirection

This article illustrates how Python implements network port forwarding and redirection. I will share it with you for your reference as follows:

"Task"

A network port needs to be forwarded to another host (forwarding), but it may be a different port (redirecting).

[solution]

Two classes that use the threading and socket modules will do the port forwarding and redirection we need.

#encoding=utf8
#author: walker " Python Cookbook ( 2rd )" 
#date: 2015-06-11
#function:  Network port forwarding and redirection (applicable to python2/python3 ) 
import sys, socket, time, threading
LOGGING = True
loglock = threading.Lock()
# Print log to standard output 
def log(s, *a):
  if LOGGING:
    loglock.acquire()
    try:
      print('%s:%s' % (time.ctime(), (s % a)))
      sys.stdout.flush()
    finally:
      loglock.release()
class PipeThread(threading.Thread):
  pipes = []   # Static member variable that stores the thread number of the communication 
  pipeslock = threading.Lock()
  def __init__(self, source, sink):
    #Thread.__init__(self) #python2.2 Previous version applicable 
    super(PipeThread, self).__init__()
    self.source = source
    self.sink = sink
    log('Creating new pipe thread %s (%s -> %s)',
        self, source.getpeername(), sink.getpeername())
    self.pipeslock.acquire()
    try:
      self.pipes.append(self)
    finally:
      self.pipeslock.release()
    self.pipeslock.acquire()
    try:
      pipes_now = len(self.pipes)
    finally:
      self.pipeslock.release()
    log('%s pipes now active', pipes_now)
  def run(self):
    while True:
      try:
        data = self.source.recv(1024)
        if not data:
          break
        self.sink.send(data)
      except:
        break
    log('%s terminating', self)
    self.pipeslock.acquire()
    try:
      self.pipes.remove(self)
    finally:
      self.pipeslock.release()
    self.pipeslock.acquire()
    try:
      pipes_left = len(self.pipes)
    finally:
      self.pipeslock.release()
    log('%s pipes still active', pipes_left)
class Pinhole(threading.Thread):
  def __init__(self, port, newhost, newport):
    #Thread.__init__(self) #python2.2 Previous version applicable 
    super(Pinhole, self).__init__()
    log('Redirecting: localhost: %s->%s:%s', port, newhost, newport)
    self.newhost = newhost
    self.newport = newport
    self.sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
    self.sock.bind(('', port))
    self.sock.listen(5) # Parameters for timeout , in seconds 
  def run(self):
    while True:
      newsock, address = self.sock.accept()
      log('Creating new session for %s:%s', *address)
      fwd = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
      fwd.connect((self.newhost, self.newport))
      PipeThread(newsock, fwd).start() # Positive transfer 
      PipeThread(fwd, newsock).start() # The reverse transmission 
if __name__ == '__main__':
  print('Starting Pinhole port fowarder/redirector')
  try:
    port = int(sys.argv[1])
    newhost = sys.argv[2]
    try:
      newport = int(sys.argv[3])
    except IndexError:
      newport = port
  except (ValueError, IndexError):
    print('Usage: %s port newhost [newport]' % sys.argv[0])
    sys.exit(1)
  #sys.stdout = open('pinhole.log', 'w') # Write the log to a file 
  Pinhole(port, newhost, newport).start()

[conversation]

When you're managing a network, even a small one, port forwarding and redirection can sometimes be a big help. Applications or services that are not under your control may be hardwired to the address or port of a particular server. By inserting forwards and redirects, you can send connection requests to applications to other hosts or ports that are more appropriate.

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I hope this article is helpful for you to design Python program.