Mac listener on port 80

Question

I want to test a cloud service which calls a URL but I dont know the format of the payload. I dont particularly want to code something up I just want to verify that the caller calls the URL and I can see the shape of message it passes. I think it will be an HTTP post to a URL of my choice - in this case a DYNDNS URL.

Can anybody suggest an appropriate bit of software to listen on port 80 of my mac and dump everything that comes through that port so I can see the URL / data passed?

Answer 1

Netcat can listen on a port and show you what arrives quite easily. It is installed on a Mac OSX as plain nc. See documentation here and here.

Try this in a Terminal window:

man nc

And:

nc -l 80

You may need sudo on the front of that because 80 is a privileged port.