def proceed(protos, port):
            """
            Send several IOCPReactor's buffers' worth of data.
            """
            self.assertTrue(protos[0])
            self.assertTrue(protos[1])
            protos = protos[0][1], protos[1][1]
            protos[0].transport.write(b'x' * (2 * 4096) + b'y' * (2 * 4096))
            return (sf.stop.addCallback(cleanup, protos, port)
                           .addCallback(lambda ign: reactor.stop()))

            Send several IOCPReactor's buffers' worth of data.
            
stackoverflow/venv/lib/python3.6/site-packages/twisted/internet/test/test_tcp.py