I have a computer located on a Internet network that has some security policies, which I don't have control over. I am looking for a program, user script, or web service that can give me a list of which ports are open for outbound connections (outbound connections = connections from my computer to a server located outside my computer's network).

It should work on Microsoft Windows or Linux. Any price or license is fine.

  • 1
    I could imagine a tool that tries to connect to an external server (probably maintained by this tool's maintainers) that would listen for connection on every single port. Would that be OK?
    – Nicolas Raoul
    Commented Oct 20, 2017 at 3:02
  • @NicolasRaoul yes that'd be ok. I have added one answer doing this. Commented Oct 20, 2017 at 3:18

1 Answer 1


The website portquiz.net can be used to check which ports are open for outbound connection, e.g. as follows (I took the command from http://thomasmullaly.com/2013/04/13/outgoing-port-tester/):

sudo apt-get install -y nmap
nmap -Pn --top-ports 1000 portquiz.net

Another way to do so, from https://gist.github.com/enginefeeder101/0805faf3862d88a97d66:


  LC_ALL=C nc -vzw5 portquiz.net $1 2>&1 | grep -v 'Connection timed out'

N=50                               # Specify number of ports to check at once
  for port in {1..65535}; do       # Specify port range to check here
    ((i=i%N)); ((i++==0)) && wait
    task "$port" &
  • 1
    Very cool that portquiz.net is a free service :-)
    – Nicolas Raoul
    Commented Oct 20, 2017 at 3:21

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