As shawnz hinted at there is a protocol dance that happens before the data is sent over. I don't know exactly what it consists of, but I suspect it's more than

As shawnz hinted at there is a protocol dance that happens before the data is sent over. I don't know exactly what it consists of, but I suspect it's more than just tcp-level responses saying the port is open and ready to receive. Playing along in that dance is arguably unethical and shows intent.