很简单的需求，自己写个类似iptables那样的dnat端口转发，简单实现像lvs那样的nat模式的端口的负载分发，当然性能堪忧哈~

这个例子是 监听 本地ip的9999端口，然后映射到另一个端口上，也可以利用random参数，进行多个端口的轮训，当然他的算法和性能简单，不能和lvs 相比了。

映射的版本：

执行方法：python th.py 8888 10.10.10.63 80

#!/usr/bin/env python#python th.py 8888 10.10.10.63 80import sys, socket, time, threadingloglock = threading.Lock()def log(msg):loglock.acquire()try:print '[%s]: \n%s\n' % (time.ctime(), msg.strip())sys.stdout.flush()finally:loglock.release()class PipeThread(threading.Thread):def __init__(self, source, target):threading.Thread.__init__(self)self.source = sourceself.target = targetdef run(self):while True:try:data = self.source.recv(1024)log(data)if not data: breakself.target.send(data)except:breaklog('PipeThread done')class Forwarding(threading.Thread):def __init__(self, port, targethost, targetport):threading.Thread.__init__(self)self.targethost = targethostself.targetport = targetportself.sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)self.sock.bind(('0.0.0.0', port))self.sock.listen(10)def run(self):while True:client_fd, client_addr = self.sock.accept()target_fd = socket.socket(socket.AF_INET, socket.SOCK_STREAM)target_fd.connect((self.targethost, self.targetport))log('new connect')# two direct pipePipeThread(target_fd, client_fd).start()PipeThread(client_fd, target_fd).start()if __name__ == '__main__':print 'Starting'import systry:port = int(sys.argv[1])targethost = sys.argv[2]try: targetport = int(sys.argv[3])except IndexError: targetport = portexcept (ValueError, IndexError):print 'Usage: %s port targethost [targetport]' % sys.argv[0]sys.exit(1)#sys.stdout = open('forwaring.log', 'w')Forwarding(port, targethost, targetport).start()

附带负载的版本：

#!/usr/bin/env pythonimport sys, socket, time, threadingloglock = threading.Lock()def log(msg):loglock.acquire()try:print '[%s]: \n%s\n' % (time.ctime(), msg.strip())sys.stdout.flush()finally:loglock.release()class PipeThread(threading.Thread):def __init__(self, source, target):threading.Thread.__init__(self)self.source = sourceself.target = targetdef run(self):while True:try:data = self.source.recv(1024)log(data)if not data: breakself.target.send(data)except:breaklog('PipeThread done')class Forwarding(threading.Thread):def __init__(self, port, targethost, targetport):number = random.randint(1,2)numbers = '%d' %numberportlist={'1':80,'2':81}host='10.10.10.63'threading.Thread.__init__(self)self.targethost = targethostself.targetport = portlist[numbers]self.sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)self.sock.bind(('0.0.0.0', port))self.sock.listen(10)def run(self):while True:client_fd, client_addr = self.sock.accept()target_fd = socket.socket(socket.AF_INET, socket.SOCK_STREAM)target_fd.connect((self.targethost, portlist[numbers]))log('new connect')# two direct pipePipeThread(target_fd, client_fd).start()PipeThread(client_fd, target_fd).start()if __name__ == '__main__':print 'Starting'import sysimport randomnumber = random.randint(1,2)numbers = '%d' %number#sys.stdout = open('forwaring.log', 'w')portlist={'1':80,'2':81}host='10.10.10.63'Forwarding(9999,host, portlist[numbers]).start()

对于性能要求高的，可以试试twisted端口转发的代码。

调优方向  I/O模型，比如阻塞、非阻塞和反应式（select,poll,WaitForMultipleObject)

现在用gevent比较多，一是gevent性能会更好一些，而且用同步的方式来实现异步(使用greenlet)，twisted中defer 和callback 会把逻辑打散。当初从twisted转到gevent最主要的原因是在twisted上很难实现多进程。gevent不好的地方就是它的mongkey_patch 有时候会带来一些奇怪的问题。

个人感觉，twisted的优点是程序的各种设计，要是针对于咱们这个映射需求的话，推荐使用gevent网络并发框架。  这个也是我较常用的。

from twisted.internet.protocol import Protocol,ClientCreatorfrom twisted.internet import reactorfrom twisted.protocols.basic import LineReceiverfrom twisted.internet.protocol import Factory,ClientFactoryclass Transfer(Protocol):def __init__(self):passdef connectionMade(self):c = ClientCreator(reactor,Clienttransfer)c.connectTCP("10.10.10.63",80).addCallback(self.set_protocol)self.transport.pauseProducing()def set_protocol(self,p):self.server = pp.set_protocol(self)def dataReceived(self,data):self.server.transport.write(data)def connectionLost(self,reason):self.transport.loseConnection()self.server.transport.loseConnection()class Clienttransfer(Protocol):def __init__(self):passdef set_protocol(self,p):self.server = pself.server.transport.resumeProducing()passdef dataReceived(self,data):self.server.transport.write(data)passfactory = Factory()factory.protocol = Transferreactor.listenTCP(9999,factory)reactor.run()

完成 ！