client.py

from twisted.internet.protocol import Protocol, ClientCreator
from twisted.internet import reactor

class TestProtocol(Protocol):
    def connectionMade(self):
        self.transport.write("1234" * 1048576)
        self.transport.loseConnection()

    def connectionLost(self, reason):
        reactor.stop()

ClientCreator(reactor, TestProtocol).connectTCP("localhost", 4321)
reactor.run()

server.py

from twisted.internet import iocpreactor
iocpreactor.install()

from twisted.internet.protocol import Protocol, Factory
from twisted.internet import reactor

class TestProtocol(Protocol):
    total = 0

    def dataReceived(self, data):
        self.total += len(data)

    def connectionLost(self, reason):
        print self.total

class TestFactory(Factory):
    protocol = TestProtocol

reactor.listenTCP(4321, TestFactory())
reactor.run()