Having problems accessing port 5000 in Vagrant

Question

I am trying to teach myself Flask in a Vagrant environment. I understand that Flask runs a server on port 5000 by default. In my Vagrantfile I have:

config.vm.network :forwarded_port, guest: 80, host: 8080
config.vm.network :forwarded_port, guest: 5000, host: 5000

I have a simple tutorial Flask app:

from flask import Flask 
app = Flask(__name__)

@app.route('/hello')
def hello_world():
    return 'Hello world!'

if __name__ == '__main__':
    app.run(debug=True)

Yet when I run python hello.py in my Vagrant environment and subsequently go to 127.0.0.1:5000/hello in Chrome on my desktop, I can't connect.

I don't know nearly enough about networking. What am I missing?

Answer 1

You possibly need to get Flask to serve on an externally-visible URL: see the docs

Answer 2

If you are accessing from Chrome in your desktop, you are technically accessing from a different computer (hence you need to place host='0.0.0.0' as argument to app.run() to tell the guest OS to accept connections from all public (external) IPs.

This is what worked for me (for both 127.0.0.1:5000/hello and localhost:5000/hello in Chrome):

from flask import Flask
app = Flask(__name__)

@app.route("/hello")
def hello():
    return "Hello World!"

if __name__ == "__main__":
    app.run(host='0.0.0.0')

Answer 3

This may be caused by Vagrant (VirtualBox) NAT Port forwarding not working properly (port conflicts).

To narrow down the issue, you may want to make sure that port 5000 is open correctly on both end, this can be done by using nmap, nc (netcat) or netstat etc.

e.g. on host

nmap 127.0.0.1

nc -vz 127.0.0.1 5000

curl http://127.0.0.1:5000

Within the guest

nmap GUEST_IP

nc -vz GUEST_IP 5000

curl http://GUEST_IP:5000

NOTE: GUEST_IP is most likely in the 10.0.2.0/24 network (vbox NAT engine default).

Running these commands on both your host and within the VM (guest box) will tell you if the ports are open.

Make sure your python hello world binds NOT ONLY to the loopback device so that it can serve requests from external clients.

Use lsof -i :5000 or netstat -nap | grep :5000 to determine which program is binding the port for further troubleshooting.

Answer 4

Do you have curl installed in your vagrant box? If not install it and try curl http://127.0.0.1:5000/hello. If you get a response and you see Hello world! in your console, then on flask side everything is fine. Back to the virtual box - When you open the network settings, from what you said above, I assume you are using a NAT address. In that case you will need to set the host address to 127.0.0.1, port 5000, leave the guest address empty and put port 5000 again and that should do the trick(port forwarding). One thing I've noticed about vagrant in those situations is that it works best if you use virtualhosts. Take a look here.

Answer 5

I was using Vagrant and solved it by adding this line of code to Vagrantfile:

  config.vm.network "forwarded_port", guest: 5000, host: 5000, host_ip: "127.0.0.1"

Answer 6

make sure to 'vagrant reload' after you change your Vagrantfile