How to implement network port forwarding and redirection in Python

The examples in this article describe how Python implements network port forwarding and redirection. Share it with everyone for your reference, the details are as follows:

[Task]

Need to forward a certain network port to another host (forwarding), but it may be a different port (redirecting).

[Solution]

Two classes using the threading and socket modules can complete the port forwarding and redirection we need.

#encoding=utf8
#author: walker摘自《Python Cookbook（2rd）》
#date: 2015-06-11
#function: 网络端口的转发和重定向（适用于python2/python3）
import sys, socket, time, threading
LOGGING = True
loglock = threading.Lock()
#打印日志到标准输出
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 = []   #静态成员变量，存储通讯的线程编号
  pipeslock = threading.Lock()
  def __init__(self, source, sink):
    #Thread.__init__(self) #python2.2之前版本适用
    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之前版本适用
    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) #参数为timeout，单位为秒
  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() #正向传送
      PipeThread(fwd, newsock).start() #逆向传送
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') #将日志写入文件
  Pinhole(port, newhost, newport).start()

[Discussion]

When you are managing a network, even a small network, port forwarding and redirection Functions can sometimes be of great help to you. Some applications or services that are not under your control may be hard-wired to a specific server address or port. By inserting forwards and redirects, you can send connection requests for your application to other, more appropriate hosts or ports.

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