Telnet to determine whether the port is open

Telnet port is a port not used by many webmasters. In many cases, we use some tools to close the port. How can we determine whether the telnet port is closed, I have collected some methods below.

How can I check the port opening status by using the telnet ip port number?

If the port is opened, it is directed to the port.

Enter the telnet ip port number in cmd. Two results are returned,

One is: connecting to (ip)... cannot open the connection to the host, in the port (port number): Connection Failed
This is the result of the port not opened for this IP address.

The other method opens a new cdm window and closes the original window, which indicates that the window is open.

If the telnet interface is black and the cursor is flashing, the port is open.

Test

Requirement: If a remote server runs a service on a port, You need to test whether the service exists.

If only the ip address is specified for the telnet command, port 23 on the peer end is connected by default.

 

If a port is specified, connect to the corresponding port.

The telnet ip port command can be used to test whether a port on the server is opened.

For example:

C:/Users/Administrator> telnet www.baidu.com 80

If the port is open, a blank screen is displayed, indicating that the connection is successful.

 

Otherwise, the connection fails.

C:/Users/Administrator> telnet www. bKjia. c0m 80666
Connecting www. bKjia. c0m... cannot open the connection to the host. Port 80666: Connection Failed