Can a tkinter application use httpServer?

Question

I currently have the below code which can be used as a demo. The code is set up to create a Tkinter window with a button. When the button is pushed it starts a HttpServer on the localhost. The issue that Im running into is that the GUI goes into a Frozen / Stalled / Crashed state and I'm not understanding why. I realize that Tkinter is ran in a single thread but not sure how a single thread would affect this.

def OpenUrl():
    run()

class server_callback(BaseHTTPRequestHandler):

  def do_GET(self):
        # Send response status code
        self.send_response(200)
        # Send headers
        self.send_header('Content-type','text/html')
        self.end_headers()
        # Send message back to client
        message = "You can now close this Browser session!"
        # Write content as utf-8 data
        self.wfile.write(bytes(message, "utf8"))
        return

def run():
  print('starting server...')
  server_address = ('127.0.0.1', 8080)
  httpd = HTTPServer(server_address, server_callback)
  print('running server...')
  httpd.serve_forever()

root = Tk()
frame = Frame(root)
frame.pack()
button = Button(frame, text="CLICK", command=OpenUrl)
button.pack()
root.mainloop()