Advice 1: How to find closed ports

Often there are situations when the installed application is not performing any functions assigned to it. One possible cause is that the port on which the program receives/sends the packets, necessary for its operation, is closed. And how to find closed ports?
How to find closed ports
The port may be closed as the modem / router and the provider side. In addition, it can be blocked by your firewall. Using standard Windows tools, you can check whether the closed port that the program uses for its operation.
In order to check open/closed ports in Windows, you must use the command line. To run press the key combination "Windows+R". After these steps, a window will open. It is necessary to enter "cmd". Then press "Enter".
The screen will appear a black window, which experts call the Windows command prompt. You can now run the very tool that will allow you to view a list of closed ports. Enter in the command prompt "netstat".
After typing, press "Enter". In the command prompt window will display information about all the open ports on your computer. This will be followed by the domain name of your personal computer and are separated from it by a colon. Note that all portsthat are not specified in this list are private. And if a port that your app uses included in this list, it will be necessary to close the application is able to function normally.
If the information provided isn't sufficient, you can explore all the possibilities of the utility "netstat", by running it with –h. This means that in command prompt you need to enter command "netstat -h". Then in the window that appears you will see help on the program "netstat".
Useful advice
Also there is a utility called "Windows Worms Doors Cleaner", which can not only show the open and closed TCP/UDP ports, but also to close the open port. Thus, you can further protect your computer from various online threats, as well as numerous viruses. The program "NetStat Agent 2.0" can replace the built-in "netstat".

Advice 2: How to find out what ports the program uses

On the computer at the same time operates a variety of programs. If the program uses Internet connection, it is allocated a specific port. Sometimes the user may need to control which port is used by one or the other program.
How to find out what ports the program uses
The need to determine which ports uses the program (or any program uses ports), typically occurs in the case of suspected infection by computer Trojans. If you notice something suspicious, open a command prompt: "start" – "All programs" – "Accessories" – "Command prompt".
At the command prompt command tasklist and hit Enter. You will get information about all running system processes. Note the PID is the process ID. It will help to determine which program uses a particular port.
In command prompt type netstat –aon and press Enter. You will see a list of current connections. In the column "Local address" at the end of each line indicates the port number. In the graph the PID specified process IDs. Looking at the port number and the corresponding PID, go to the processes list and the ID number will determine which process is using this port.
If you are unable to name the process to understand which program it belongs to, use the one suitable in this case programs. For example, a program Everest, it is also Aida64. Run the program, select "Operating system", select "Processes". In the processes list find the right and view the line of its launch. This will help to determine which program owns a process.
Use for the same purpose the program AnVir Task Manager. It allows you to track all the suspicious processes, including the process of programs linking to the Internet. All suspicious processes are highlighted in the programs list in red.
If you see that port being used unknown to you program, in the presence of the current connection in the "External address" (netstat –aon), you will see the ip address of the computer from which the connection is established. In the column "Status" will be the value ESTABLISHED – if the connection is present at the moment; CLOSE_WAIT if the connection is closed; LISTENING, if the program is waiting for connection. The latter is typical for backdoors - one of the varieties of Trojans.
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