Indeed the issue is with your call to pipe-content-length which is to be used with pipes and is not the Content-Length header returned when doing HTTP requests. The Content-Length can be found in the list of headers returned by the call to http-sendrecv (second value or b in your let-values call). You can parse these using the net/head module.
HTH Philippe On Tue, Oct 16, 2018 at 9:42 PM Chansey <[email protected]> wrote: > Hi Philippe > > I now use (copy-port ip op), it works. > > Thanks. > > But why my code above can not work? ( content-length wrong?) > > > > On Wednesday, October 17, 2018 at 3:30:05 AM UTC+8, Philippe M wrote: >> >> Hi >> >> You could simply do a (copy-port ip op) and remove the content-length >> and buffer parts i think. >> >> >> Le mar. 16 oct. 2018 à 21:17, Chansey <[email protected]> a écrit : >> >>> >>> Dear all, >>> >>> I wrote some experiment code for net/http-client. >>> >>> The purpose is downloading some images from web. >>> >>> This is my code (run on windows7 using DrRacket, version 6.12): >>> >>> #lang racket >>> >>> (require net/http-client) >>> (require "./racket-pretty-bytes/main.rkt") >>> >>> (define ip (let-values (((a b c) (http-sendrecv "www.google.com" >>> >>> "/images/branding/googlelogo/1x/googlelogo_color_272x92dp.png"))) >>> >>> c)) >>> >>> ;; different/wrong size per call??? >>> (define content-length (pipe-content-length ip)) >>> (println content-length) >>> >>> (let ([buffer (make-bytes content-length)]) >>> (read-bytes! buffer ip 0 content-length) >>> (pretty-print-bytes buffer) >>> >>> (let ((op (open-output-file "google.png"))) >>> (write buffer op) >>> (close-output-port op)) >>> ) >>> >>> >>> The problem is the content-length wrong, so the download file >>> "google.png" can not be open by image viewer. >>> >>> Is there any reference code or tutorial for downloading image and save >>> files using http-client ? >>> >>> Thanks. >>> >>> Br, >>> Chansey >>> >>> >>> -- >>> You received this message because you are subscribed to the Google >>> Groups "Racket Users" group. >>> To unsubscribe from this group and stop receiving emails from it, send >>> an email to [email protected]. >>> For more options, visit https://groups.google.com/d/optout. >>> >> -- > You received this message because you are subscribed to the Google Groups > "Racket Users" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to [email protected]. > For more options, visit https://groups.google.com/d/optout. > -- You received this message because you are subscribed to the Google Groups "Racket Users" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. For more options, visit https://groups.google.com/d/optout.
