In some situations or on some locations, I'm struggling with restricted outgoing traffic. For example a restricted LAN where outgoing traffic is only allowed on limited ports.

I know how to check or test my connection or network for incoming traffic on various ports. But I can't find how to do the opposite: checking on what ports I can make outgoing connections from my device.

Does anyone know how to do this? E.g. a way to probe a range of ports (regardless to what external server or IP).

I assume there a different ways to do this for different platforms: in this case I'm on OS X.

Note that I'm not dealing with a firewall or restriction on my own device, it's not a matter of local system configuration. I'm connected through a LAN which appears to have a very restrictive firewall or router or something, and I need to find out to which ports I can still connect to the outside world.

closed as off-topic by Ron Maupin, Mike Pennington, Teun Vink Jun 23 '16 at 8:09

This question appears to be off-topic. The users who voted to close gave this specific reason:

  • "NE is a site for to ask and provide answers about professionally managed networks in a business environment. Your question falls outside the areas our community decided are on topic. Please visit the help center for more details. If you disagree with this closure, please ask on Network Engineering Meta." – Ron Maupin, Mike Pennington, Teun Vink
If this question can be reworded to fit the rules in the help center, please edit the question.

  • Unfortunately, product or resource recommendations are explicitly off-topic here. You could try to ask this question on Software Recommendations. – Ron Maupin Jun 22 '16 at 12:43
  • @RonMaupin Ok, I see. Would it be OK if I change my inquiry to "how to" rather than asking for a specific tool or script? If there is some fancy shell command or other technical solution to this, that would suit my need just as well. – RocketNuts Jun 22 '16 at 12:50
  • You can certainly edit your question to ask how, but I don't think you would like an answer which says you need a firewall which filters in both directions. That seems to leave you in the same place you are now, asking which one to use. – Ron Maupin Jun 22 '16 at 12:55
  • I actually don't need a firewall, it appears (in some cases) there is a firewall in place on the LAN I'm connected to, and I'm just trying to find out which ports are still open / accessible (for outgoing traffic). So I'll give it a try. – RocketNuts Jun 22 '16 at 12:57
  • If you need help with your OS, you could ask on the SE site for the OS, e.g. Ask Different for OSX, or on Super User. Host configurations are also off-topic here. – Ron Maupin Jun 22 '16 at 13:01

Use a program like NMAP to determine what ports are open to what addresses. Security operations(assuming your network has a security team) may not appreciate this as it will look suspicious when you are scanning networks for open ports.


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