Send: HI
		receive		HELLO (proceed)
		else 		show communication error
	Send: BANKACCOUNTNUMBER:#
		receive		CONTINUE (proceed)
		receive		STOLEN, destroy card
		receive		BLOCKED, show card blocked error
		receive		INVALID, show card error
		else		show communication error
	Send: PIN:#,ATTEMPT:#
		receive		CONTINUE (proceed)
		receive		INVALID, try again
		receive		BLOCKED, too many attempts, show blocked error
		else		show communication error
	Send: GETBALANCE:
		receive		BALANCE:#, show balance
		else		show communication error
	Send: WITHDRAWREQUEST:#
		receive		APPROVED (give user requested amount, send BYE)
		receive		BALANCEERROR, show not enough money error
		receive		OTHERERROR, show generic error message
		else		show communication error
	Send: BYE:
		receive		CYA, properly close socket
		else		silent error, destroy socket

	Voorbeeld:
		Machine				Central Computer
		HI
							HELLO
		BANKACCOUNTNUMBER:111199444
							CONTINUE
		PIN:0000,ATTEMPT:0
							CONTINUE
		WITHDRAWREQUEST:900
							APPROVED
		BYE
							CYA