I'm running HTTPServerHelloWorld on my mbed. I can read the output from the mbed on my Teraterm window with the IP address of 192.168.100.2, just as I specified in the code before I compiled it.

How do I figure out which port the PC is listening to the mbed on?

You can:

1. Try to catch it in the act with "netstat -an" at a command prompt
2. Install WireShark and capture the network traffic and look at that
3. Install "curl" and use that in a verbose mode (this is a great tool for server development, as is WireShark)

P.S. - The PC is not listening to the mbed - it's the other way around.

running HTTPServerHelloWorld

The Mbed is listening on port 80 (HTTP port) , you can verify this by typing 192.168.100.2:80 in your browser you will get the request response will be

200 OK Content-Type: text/html Connection: Close your html running in serverhelloworld here

if you try the alternate HTTP port (8080) in your browser (192.100.0.2:8080 or any other port) you will rightly get no response.