def run(self):
try:
server_address = ('0.0.0.0', 8000) # Use port 8000 by default.
httpd = HTTPServer(server_address, PreviewServer.RequestHandler)
except OSError: # If port is not available,
server_address = ('0.0.0.0', 0) # use random free port number.
httpd = HTTPServer(server_address, PreviewServer.RequestHandler)
httpd.site = self.site # Make site object available to the handler
self.port = httpd.server_port
httpd.serve_forever()
