1, install telnet. Under my win7 is no telnet, telnet prompt does not enter this command in cmd. So we go to Control Panel ----> Programs ----> to open or close the windows function. And then wait for a period of time, out of the box in the telnet client and telnet server check on the other do not control, and then click OK. This installed component of the telnet.
2, you can start testing whether to open a port, for example, I measured 80 is 10.10.11.245 this port. In the input cmd
Start / Telnet 10.10.11.245 80 min
then there will be a window is minimized, you later on, if the window is automatically closed, indicating port is closed or not ping a host, otherwise the port is open.
For example, the port 80 is open, so it is shown in the window, or the window is closed.
3, you can use your machine to do the experiment. Enter the netstat -anp tcp under CMD can see what the current host tcp open port.