Question

I need run tornado web server in a random port.

Usually if a socket is bind to the port 0 the os assign a random port.

import socket
s = socket.socket()
s.bind(('',0))
print s.getsockname()
('0.0.0.0', 39727)

where 39727 is the port assigned by the OS.

how can I get this behavior using tornado?

Answer 1

Tornado passes on the port, you can call bind_sockets with a port of 0, like this:

import tornado.httpserver
import tornado.ioloop
import tornado.netutil
import tornado.web

app = tornado.web.Application()
sockets = tornado.netutil.bind_sockets(0, '')
server = tornado.httpserver.HTTPServer(app)
server.add_sockets(sockets)

for s in sockets:
    print('Listening on %s, port %d' % s.getsockname()[:2])
tornado.ioloop.IOLoop.instance().start()

Note that you’ll get different port numbers for IPv4 and IPv6. If you want IPv4 and IPv6 to be on the same port, either try port numbers yourself, or supply a list with your own socket created as in the question (create an IPv6 socket with IPV6_V6ONLY set to 0 to get both IPv6 and IPv4 on the same socket) in the place of sockets in the above.