Hello
I know how to send unsigned short integer value with big-endian via TCP now.
But when trying to parse the unsigned short integer from bytes array returned by net-receive, I am stuck again.
Below is my codes, the server sends 3 bytes to client app written by newlisp.
The first byte is 0x01, the following two bytes are in big-endian, they represent one unsigned short integer here. I try to parse them using get-char twice. But it seems wrong.
(define (receive-challenge-string socket)
;; receive head
(unless (net-receive socket head 3) (quit-for-error))
(unless (= (get-char (address head)) 1) (println "SOH in challenge message is wrong"))
(println
(unpack ">u" (get-char (+ (address head) 1)) (get-char (+ (address head) 2)))
))
Unless you need an offset into the buffer - head - received by 'net-receive', you don't need 'address' and when using 'unpack' you don't need 'get-char'.
Just do:
" 00{"
> (unpack ">u" head) ; <--- this is all you need
(123)
>
Thank you lutz!
After removing get-char, I got the number 19 from server. Here are my correct codes below:
(define (receive-challenge-string socket)
;; receive head
(unless (net-receive socket head 3) (quit-for-error))
(unless (= (get-char (address head)) 1) (println "SOH in challenge message is wrong"))
(println (unpack ">u" (+ (address head) 1))))
Then it prints the correct number now:
(19)
You could also unpack both numbers at once:
(1 19)
> (unless (= (first result) 1) (println "SOH wrong"))
true
>