Downloading Files - QB64 Wiki

Downloading Files

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HTTP/1.1 protocol downloads can be done using a GET request using the following format without HTTP:// in the url:

CRLF$ = CHR$(13) + CHR$(10) Request$ = "GET " + File_Path + " HTTP/1.1" + CRLF$ + "Host:" + Web_Address + CRLF$ + CRLF$

Two carriage returns end the request to the client URL. The header that is returned from the site also ends with two carriage returns when there are no errors. The header will also include the requested file's byte size after "content-length:" as below:

HTTP/1.1 200 OK Server: dbws Date: Tue, 25 Oct 2011 04:41:03 GMT Content-Type: text/plain; charset=ascii Connection: keep-alive content-length: 4087 x-robots-tag: noindex,nofollow accept-ranges: bytes etag: 365n pragma: public cache-control: max-age=0

Each row of text response sent is ended with a carriage return with the end of header having two. After that comes the file data.
It is recommended that data be loaded immediately by using a GET loop so that connections are not dropped during a delay.


A "raw" Download function that downloads an image directly off of a web page using the image name on that page.

IF Download("www.qb64.net/qb64.png", "qb64logo.png", 10) THEN ' timelimit = 10 seconds SCREEN _LOADIMAGE("qb64logo.png",32) ELSE: PRINT "Couldn't download QB64 logo." END IF SLEEP SYSTEM ' ---------- program end ----------- FUNCTION Download (url$, file$, timelimit) ' returns -1 if successful, 0 if not url2$ = url$ x = INSTR(url2$, "/") IF x THEN url2$ = LEFT$(url$, x - 1) client = _OPENCLIENT("TCP/IP:80:" + url2$) IF client = 0 THEN EXIT FUNCTION e$ = CHR$(13) + CHR$(10) ' end of line characters url3$ = RIGHT$(url$, LEN(url$) - x + 1) x$ = "GET " + url3$ + " HTTP/1.1" + e$ x$ = x$ + "Host: " + url2$ + e$ + e$ PUT #client, , x$ t! = TIMER ' start time DO _DELAY 0.05 ' 50ms delay (20 checks per second) GET #client, , a2$ a$ = a$ + a2$ i = INSTR(a$, "Content-Length:") IF i THEN i2 = INSTR(i, a$, e$) IF i2 THEN l = VAL(MID$(a$, i + 15, i2 - i -14)) i3 = INSTR(i2, a$, e$ + e$) IF i3 THEN i3 = i3 + 4 'move i3 to start of data IF (LEN(a$) - i3 + 1) = l THEN CLOSE client ' CLOSE CLIENT d$ = MID$(a$, i3, l) fh = FREEFILE OPEN file$ FOR OUTPUT AS #fh: CLOSE #fh 'Warning! Clears data from existing file OPEN file$ FOR BINARY AS #fh PUT #fh, , d$ CLOSE #fh Download = -1 'indicates download was successfull EXIT FUNCTION END IF ' availabledata = l END IF ' i3 END IF ' i2 END IF ' i LOOP UNTIL TIMER > t! + timelimit ' (in seconds) CLOSE client END FUNCTION

Code by Galleon


Downloading a BINARY image file from a download link using GET # which requires the "content-length" in header.

DEFINT A-Z CR$ = CHR$(13) + CHR$(10) 'crlf carriage return line feed characters ' Change this to the file's public link DownFile$ = "http://a5.sphotos.ak.fbcdn.net/hphotos-ak-snc7/293944_10150358253659788_151813304787_8043392_486717139_n.jpg?dl=1" ' Get base URL BaseURL$ = DownFile$ IF INSTR(BaseURL$, "http://") THEN BaseURL$ = RIGHT$(BaseURL$, LEN(BaseURL$) - 7) 'trim http:// Path$ = MID$(BaseURL$, INSTR(BaseURL$, "/")) 'path to file BaseURL$ = LEFT$(BaseURL$, INSTR(BaseURL$, "/") - 1) 'site URL ' Connect to base URL PRINT "Connecting to "; BaseURL$; "..."; Client& = _OPENCLIENT("TCP/IP:80:" + BaseURL$) IF Client& = 0 THEN PRINT "Failed to connect...": END PRINT "Done." ' Send download request PRINT "Sending download request..."; Request$ = "GET " + Path$ + " HTTP/1.1" + CR$ + "Host:" + BaseURL$ + CR$ + CR$ PUT #Client&, , Request$ PRINT "Done." ' Download the header PRINT "Getting HTML header..."; Dat$ = "" DO _LIMIT 20 GET #Client&, , gDat$ Dat$ = Dat$ + gDat$ LOOP UNTIL INSTR(Dat$, CR$ + CR$) ' Loop until 2 CRLFs (end of HTML header) are found PRINT "Done." ' Get file size FileSizePos = INSTR(UCASE$(Dat$), "CONTENT-LENGTH: ") + 16 FileSizeEnd = INSTR(FileSizePos, Dat$, CR$) FileSize& = VAL(MID$(Dat$, FileSizePos, (FileSizeEnd - FileSizePos) + 1)) PRINT "File size:"; FileSize& PRINT "Downloading file..."; ' Trim off HTML header EndHeaderPos = INSTR(Dat$, CR$ + CR$) + 4 Dat$ = RIGHT$(Dat$, (LEN(Dat$) - EndHeaderPos) + 1) ' Get the file name tucked at the end of the URL if necessary FOR S = LEN(DownFile$) TO 1 STEP -1 IF MID$(DownFile$, S, 1) = "/" THEN OutFile$ = RIGHT$(DownFile$, (LEN(DownFile$) - S)) EXIT FOR END IF NEXT S ' Remove some kind of tag at the end of the file name in some URLs IF INSTR(OutFile$, "?") THEN OutFile$ = LEFT$(OutFile$, INSTR(OutFile$, "?") - 1) ' Download the rest of the data OPEN OutFile$ FOR OUTPUT AS #1: CLOSE #1 'Warning! Clears data from an existing file OPEN OutFile$ FOR BINARY AS #1 'write data to binary image file DO _LIMIT 20 PUT #1, , Dat$ GET #Client&, , Dat$ LOOP UNTIL LOF(1) >= FileSize& CLOSE #1, #Client& PRINT "Done!"

Adapted from code by Jobert14
Note: Some download links require that a tag be added after the file name. Remove that tag if it will be used as the file name.


Downloading a sequencial text file from a Drop Box download link using HTTP GET and the TCP/IP GET statement.

CrLf$ = CHR$(13) + CHR$(10) ' carriage return + line feed ASCII characters Host = _OPENHOST("TCP/IP:319") IF Host THEN PRINT "> Server started succesfully." '// Change this to the file's public link IP_File$ = "dl.dropbox.com/u/8440706/QB64.INI" 'a Drop Box link URL$ = LEFT$(IP_File$, INSTR(IP_File$, "/") - 1) Path$ = MID$(IP_File$, INSTR(IP_File$, "/")) Client& = _OPENCLIENT("TCP/IP:80:" + URL$) IF Client& THEN Request$ = "GET " + Path$ + " HTTP/1.1" + CrLf$ + "Host:" + URL$ + CrLf$ + CrLf$ PUT #Client&, , Request$ DO: _LIMIT 20 ' load response header GET #Client&, , Dat$ Header$ = Header$ + Dat$ LOOP UNTIL INSTR(Header$, CrLf$ + CrLf$) ' Loop until 2 CRLFs (end of HTML header) are found PRINT "Header Done." ' Get file size from header SizePos = INSTR(UCASE$(Header$), "CONTENT-LENGTH:") + 16 SizeEnd = INSTR(SizePos, Header$, CrLf$) FileSize& = VAL(MID$(Header$, SizePos, (SizeEnd - SizePos) + 1)) PRINT "File size is"; FileSize&; "bytes" EndPos = INSTR(Header$, CrLf$ + CrLf$) + 4 Response$ = MID$(Header$, EndPos) ' get data after header already downloaded start = 1 '// Get file name from original URL path if necessary DO '// Change this to destination local file name and path... posit = INSTR(start, IP_File$, "/") IF posit THEN lastpos = posit: start = posit + 1 LOOP UNTIL posit = 0 File$ = MID$(IP_File$, lastpos + 1) 'beware of tag suffixes OPEN File$ FOR BINARY AS #1 DO: _LIMIT 20 PUT #1, , Response$ GET #Client&, , Response$ LOOP UNTIL LOF(1) >= FileSize& PRINT "File download completed!" CLOSE #1 ELSE PRINT "Failed to connect." END IF ELSE PRINT "Failed to create server connection..." END IF

Code suggested by Matt Kilgore
There is no limit on file size! The QB64.INI file can be used to configure the PSPAD programming editor for QB64 keywords.


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