How to Tell if a Function Exists in an IP Address

You can determine if a remote computer is providing a given function at a given network address.

A computer can act as a server for a variety of functions, such as the capability to run commands over a Secure Shell connection. To act as a client for such a function, a client connected to the server's network needs to know the server's Internet Protocol (IP) address. The client also needs to know the port number for the function in question, as the same computer may act as server for multiple functions. You can determine if a given function is available at a given IP address/port number combination.

Instructions

1. Log into a command prompt on any computer connected to the computer whose IP address you want to query. The specific way of performing this step depends on the operating system. For example, for Linux, press "Control-Alt-F1" to bring up a text-mode login prompt, then type your username and password to log in.

2. Type the following line at the command prompt:

   nmap -p 80 192.168.75.4

   Replace "80" with the number of the port you want to ping, and "192.168.75.4" with the IP address of the computer where the port is. Press "Enter."

3. Search the output of "nmap" for the result of pinging the port. If the port is listed as "closed," there is no function provided at that port. Otherwise, "nmap" will list it as "open" and will make a (usually good) conjecture about the specific function available at the port; that will be displayed under the "service" column.

References

• Nmap:Nmap Reference Guide