Windows 7: Set a firewall to prevent other hosts from accessing a port on the host.

First, let's take a look at the inbound rules and outbound rules: Inbound means that others access you, and outbound means that you access others.
Choose Control Panel> system and security> windows Firewall ". Click "Advanced Settings" on the left-side panel to display the "Advanced Security windows Firewall" window:

Click "inbound rules" on the left, click "create rule" on the right, and select "Port ":

After "Next", select the protocol and port, such as TCP and 4000 ports:

After "Next", select "block connection ":

Next, select as needed:

Finally, set the name and click "finish ":

The new rules are enabled by default.