well if not, than here it is.
Banner Grabbing :
This is good technique to learn and can also be used to perform a manual
portscan. E.g. Telnetting to every port on a victims computer and noting down which ones
you could connect to you and what services are running. This is what hackers had
to resort to before automated portscanners were written.
Banner grabbing is the art of connecting to a certain port or service and noting
down what response you get from the port daemon (The little "prog" that listens
for connections and then sends out information accorinding to what the user
types/does). Here is an example.
The targets IP is 188.8.131.52. You need to find out what OS he is running.
Lets try some common ports that give us feedback. We'll try port 80, http. To do
this we telnet to...and so on.
If you want more details, just let me know.