pack all fields into one string buffer

[csfreebird]

I want to send a message via TCP to remote server. This message consists of a few fields, some fields are sting, some are number. My old way is to pack one field and then send it. e.g.

Code Select Expand


(define (send-message type content)
  ;; send SOH
  (unless (net-send (self 4) SOH) (throw-error (string "send soh failed: " (net-error))))
  ;; send length
  (unless (net-send (self 4) (hex-str (+ 10 (length content)) 4)) (throw-error (string "send length failed: " (net-error))))  
  ;; send type
  (unless (net-send (self 4) type) (throw-error (string "send type failed: " (net-error))))  
  ;; send content
  (unless (net-send (self 4) content) (throw-error (string "send content failed: " (net-error))))                                                                              
  ;; send checksum
  (let (checksum-value (cal-checksum (total2 (append type content))))
    (unless (net-send (self 4) (hex-str checksum-value 2)) (throw-error (string "send checksumfailed: " (net-error)))))                                                        
  ;; send ETX                                                                                                                                                                    
 (unless (net-send (self 4) ETX) (throw-error (string "send etx failed: " (net-error)))))        


But I want to pack all fields in one string buffer and send them one time. How to do this?

[csfreebird]

Got it. just use (string ) to contruct it.

Code Select Expand


(define (send-message type content)
  (letn ((checksum-value (hex-str (cal-checksum (total2 (append type content))) 2))
(str-buffer (string (pack "b" 1) (format "%s%s%s%s" (hex-str (+ 10 (length content)) 4) type content checksum-value) (pack "b" 3))))
(let (r (net-send (self 4) str-buffer))
  (if r
      (log (format "sent message succeeded, size is: %llu" r))
    (throw-error (string "send message failed: " (net-error)))))
))