When you are solving certain problems related to the Internet and computers, technical support specialists can usually ask you to check if you (and your Internet provider) have a closed port. How can you check this? After all, you need reliable information. To check if a port is open or closed, you need to use the "telnet" utility.
It is necessary
Personal Computer
Instructions
Step 1
In Windows Vista and Windows 7, the telnet utility is disabled by default (by default), and therefore, first you need to install the program itself. Installation takes less than a minute. Just go to the official website of the operating system and download the program. Next, run the installation package by clicking the "Next" tab. When the installation is complete, click the Finish button.
Step 2
If your operating system is Windows XP, then you do not need to install anything, since the utility is already there. In Windows XP, select "Start" from the start menu, then click "Run". In the small window that opens, enter the command “cmd” and click the OK button. You can also press the “Enter” key.
Step 3
If your operating system is Windows Vista or Windows 7, click the "Start" button. Next, select the Run item and enter the “cmd” command in the search field and click OK. In general, we can say that the principle of installation in all operating systems is the same, just a slightly different arrangement of the tabs.
Step 4
In the terminal window that opens, enter the command: "telnet server_name port_number". Then press the "Enter" key. All data must be correct so that the system can check all information. If the data you filled in is incorrect, the result will not be returned.
Step 5
For example, in order to check whether the port on which SMTP works is open or closed, you must enter the command in the terminal window: "telnet smtp.your_domain 25".
Step 6
If after entering the command returns an error, it means that the port is closed. And if the server prompt appears on the monitor screen (or the terminal window becomes completely empty), then the port is open. In general, we can say that almost every port is checked on the computer under this operation.
