I face some problem """"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""" from twisted.internet import defer, reactor from twisted.web import resource, server import os, sys class FileDownloadResource(resource.Resource): isLeaf = 1 fName = 'very big file size' path = 'some_path' def render(self, request): d = True if d: d = "attachment" else: d = "inline" request.setHeader("Content-type", "application/x-msdownload"); request.setHeader("Content-Disposition", d + "; filename=" + self.fName); request.setHeader("Content-Length", ' ' + str(self.getFileSize(self.path + self.fName))); request.setHeader("Content-Transfer-Encoding", "binary"); request.setHeader("Pragma", "no-cache"); request.setHeader("Expires", "0"); # print "entered render" d = defer.Deferred() d.addCallback(self.printResult, request) d.addErrback(self.printError, request) return server.NOT_DONE_YET def printError(failure, request): request.write(str(failure)) request.finish() def printResult(self, request): for line in open(self.path + self.fName, 'r'): request.write(line) request.finish() def getFileSize(self, file): size = os.path.getsize(file) return size resource = FileDownloadResource() """""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""" I don't know what am i doing please give any hint