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Asked: 2026-05-11T17:50:20+00:00

I’ve made a simple http server using Twisted, which sends the Content-Type: multipart/x-mixed-replace header.

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I’ve made a simple http server using Twisted, which sends the Content-Type: multipart/x-mixed-replace header. I’m using this to test an http client which I want to set up to accept a long-term stream.

The problem that has arisen is that my client request hangs until the http.Request calls self.finish(), then it receives all multipart documents at once.

Is there a way to manually flush the output buffers down to the client? I’m assuming this is why I’m not receiving the individual multipart documents.

#!/usr/bin/env python

import time

from twisted.web import http
from twisted.internet import protocol

class StreamHandler(http.Request):
    BOUNDARY = 'BOUNDARY'

    def writeBoundary(self):
        self.write("--%s\n" % (self.BOUNDARY))

    def writeStop(self):
        self.write("--%s--\n" % (self.BOUNDARY))

    def process(self):
        self.setHeader('Connection', 'Keep-Alive')
        self.setHeader('Content-Type', "multipart/x-mixed-replace;boundary=%s" % (self.BOUNDARY))

        self.writeBoundary()

        self.write("Content-Type: text/html\n")
        s = "<html>foo</html>\n"
        self.write("Content-Length: %s\n\n" % (len(s)))
        self.write(s)
        self.writeBoundary()
        time.sleep(2)

        self.write("Content-Type: text/html\n")
        s = "<html>bar</html>\n"
        self.write("Content-Length: %s\n\n" % (len(s)))
        self.write(s)
        self.writeBoundary()
        time.sleep(2)

        self.write("Content-Type: text/html\n")
        s = "<html>baz</html>\n"
        self.write("Content-Length: %s\n\n" % (len(s)))
        self.write(s)

        self.writeStop()

        self.finish()

class StreamProtocol(http.HTTPChannel):
    requestFactory = StreamHandler

class StreamFactory(http.HTTPFactory):
    protocol = StreamProtocol


if __name__ == '__main__':
    from twisted.internet import reactor
    reactor.listenTCP(8800, StreamFactory())
    reactor.run()
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1 Answer

  1. Editorial Team

    Using time.sleep() prevents twisted from doing its job. To make it work you can’t use time.sleep(), you must return control to twisted instead. The easiest way to modify your existing code to do that is by using twisted.internet.defer.inlineCallbacks, which is the next best thing since sliced bread:

    #!/usr/bin/env python

import time

from twisted.web import http
from twisted.internet import protocol
from twisted.internet import reactor
from twisted.internet import defer

def wait(seconds, result=None):
    """Returns a deferred that will be fired later"""
    d = defer.Deferred()
    reactor.callLater(seconds, d.callback, result)
    return d

class StreamHandler(http.Request):
    BOUNDARY = 'BOUNDARY'

    def writeBoundary(self):
        self.write("--%s\n" % (self.BOUNDARY))

    def writeStop(self):
        self.write("--%s--\n" % (self.BOUNDARY))

    @defer.inlineCallbacks
    def process(self):
        self.setHeader('Connection', 'Keep-Alive')
        self.setHeader('Content-Type', "multipart/x-mixed-replace;boundary=%s" % (self.BOUNDARY))

        self.writeBoundary()

        self.write("Content-Type: text/html\n")
        s = "<html>foo</html>\n"
        self.write("Content-Length: %s\n\n" % (len(s)))
        self.write(s)
        self.writeBoundary()


        yield wait(2)

        self.write("Content-Type: text/html\n")
        s = "<html>bar</html>\n"
        self.write("Content-Length: %s\n\n" % (len(s)))
        self.write(s)
        self.writeBoundary()

        yield wait(2)

        self.write("Content-Type: text/html\n")
        s = "<html>baz</html>\n"
        self.write("Content-Length: %s\n\n" % (len(s)))
        self.write(s)

        self.writeStop()

        self.finish()


class StreamProtocol(http.HTTPChannel):
    requestFactory = StreamHandler

class StreamFactory(http.HTTPFactory):
    protocol = StreamProtocol


if __name__ == '__main__':   
    reactor.listenTCP(8800, StreamFactory())
    reactor.run()

    That works in firefox, I guess it answers your question correctly.

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