How to detect if a port on a remote host is open?

Sometimes we want to test whether a port on the remote host is open, without using too complicated work, there is a tool that comes with windows, that is telnet. How to detect it, according to the following steps: 1. Install telnet. There is no telnet under my win7, and entering telnet under cmd prompts that there is no such command. So we go to Control Panel---->Programs---->Turn Windows features on or off. Then wait for a while, and check the telnet client and telnet server in the dialog box that comes out