Scan all ports in a CIDR block with the doscommand

Open a DOS window in Win2000 and then execute
For/L % A in (1, 1, 254) do start/MIN/low Telnet 192.168.0.% A 3389
In this way, all open ports 3389 in the 192.168.0.x segment will be exposed to hosts.
After this command is executed
254 small windows will be opened in the taskbar
Then, the window that fails the Telnet link will automatically exit in about 5 seconds.
The remaining window is the host with the corresponding port opened.
Check the title of the small window to learn the Host IP address.
If you think the machine performance is good, you can set the/low parameter.

Scan multiple ports of a host as follows:
For/L % A in (1, 1, 65535) do start/low/min Telnet 192.168.0.1%
In this way, Port 1 to port 65535 of 192.168.0.1 is scanned.

Scan all ports in a CIDR Block
For/L % A in (254, 65535) do for/L % B in (,) do start/low/min Telnet 192.168.0.% A % B
This will scan all ports 1 to 65535 in the 192.168.0.x segment.

The above commands can only be used in Win2000, because the/L accumulate parameter is an extension of Win2000.
Of course, both WINXP and win. Net can be used. I have not tried winme, because there is no winme machine.