from twisted.internet.protocol import Protocol
from twisted.internet import reactor
from twisted.internet.protocol import Factory
from twisted.internet.endpoints import TCP4ServerEndpoint

class Echo(Protocol):
       
     def __init__(self,factory):
         self.factory=factory

     def connectionMade(self):
         self.factory.numProtocols=self.factory.numProtocols+1
         self.transport.write("welcome!\nthere are currently %d open connections.\n"%(self.factory.numProtocols,))

     def dataReceived(self,data):
         mydata=data.strip()
	 if mydata!="quit" and  mydata!="quit\r\n" and mydata!="quit\r": 
              self.transport.write(data)
         else:
              self.transport.write("byebye\n")
              self.transport.numProtocols=self.factory.numProtocols-1
              self.transport.loseConnection()
     def connectionLost(self, reason):
         self.factory.numProtocols = self.factory.numProtocols - 1

class EchoFactory(Factory):
     numProtocols=0
     def __init__(self):
         self.myfactory=self
     def buildProtocol(self,addr):
         return Echo(self.myfactory)    

endpoint=TCP4ServerEndpoint(reactor,8001)
endpoint.listen(EchoFactory())
reactor.run()

输入quit退出连接，统计连接数量。