Advice 1: How to determine closed ports

Any program that uses the local network or the Internet, making it through any port. A port is a logical system address, the memory through which data is exchanged. Closed are those portswhich cannot create a connection. The reason may be in the settings of the firewall of your computer or server from your provider. Usually, the subscribers can contact your operator or using additional software.
How to determine closed ports
Instruction
1
Run the program, which will be the server for the data. In other words, to check availability or openness of the port, you need a program which will connect customers from the network. For example, you want to play a network game. So, you need to create a server of this game on your PC will connect to the other players. The same applies to other programs designed for operation on the network.
2
Click "start" and click "Run." In the command box, type cmd, you open the system console Windows. In the black window, type netstat-b this will start the test currently open and used ports, with the name of the processes. You will see a list in the form of columns with headers: Name, Local address, Foreign address, State. The name means the name of the communication Protocol, TCP or UDP. Also in this column is written the name of the process that is associated with this connection.
3
Local address is your computer and the port number on it. External address points to the computer that established the current connection. In the column "Status" may be the record Established — it means the port is opened successfully and connection is established. Message, Closed, Close_wait means that the packet exchange has completed successfully. All other ports are currently inactive and closed, that is, produce no data exchange.
4
Note that checking the netstat utility only concerns your computer and does not apply to servers of the ISP. This means that you will not be able in this way to find out blocked ports. Most companies restrict the use of programs for listening or port scanning. However, knowing the exact room and wanting to define a closed port or open, you can use the online verification services.
5
Launch any browser and go to the page http://www.whatsmyip.org/port-scanner/ or http://portscan.ru. Enter the window of the test instrument you are interested in the number and press Enter or "Verify". After a few seconds you will get an answer about the availability or unavailability of the port.

Advice 2: How to check the port is available

The solution of the problem of the availability check in port operating system Microsoft Windows 7 can be found in using the Microsoft Telnet client that enables users to establish a TCP connection to the local host via 127.0.0.1 verifiable port.
How to check the port is available
Instruction
1
The main menu of the operating system Microsoft Windows 7 by clicking "start" and change the value to telnet to the box of the search string to perform the operation of starting the client.
2
Click "Find" and open the context menu of a found item telnet.exe click the right mouse button.
3
Specify the "Run as administrator" and confirm your choice in the request window "UAC" by clicking "Yes".
4
Specify the value of the administrator password in the pop-up window prompted to confirm their authority or use an alternative method of starting the client.
How to check the port is available
5
The main menu of the operating system by pressing the "start" button, and specify a value cmd.exe in the text box of the search string.
6
Click "Find" and open the context menu of a found item, click the right mouse button.
7
Specify the "Run as administrator" and confirm your choice with the introduction of the password values in the request window system.
8
Specify a value in the text box, telnet command line and press Enter to confirm the command.
9
Enter a value of o or open 127.0.0.1 in the window command interpreter of the Microsoft Telnet client and confirm the command by pressing the function key Enter.
10
Wait for the window cleaning client (in the case of a connection) or the message on impossibility to establish the connection (if local port is unavailable subject to verification) and use the following commands to define the necessary settings:
- ?/h is for help;
- to end the active connection;
- u - to reset;
- d - to display the parameters;
- st to display the current status;
- o port_number - connects to the selected port;
- sen - to send the selected rows to the server.
- q - for the completion of the client;
- set - to determine the necessary parameters.
How to check the port is available

Advice 3: How to watch closed ports

When you connect to the Internet, the operating system allocates network programs ports, through which is receiving and sending data. The port can be opened or closed. Sometimes the user may need to monitor the status of ports.
How to watch closed ports
Instruction
1
When talking about the port that it is open, it means that it is currently using some kind of program. To connect with the network can be used more than 65 thousand ports. Those ports, which are currently not used, are closed. Therefore, to see the closed ports as such it is impossible, in the analysis of network connections, watch open ports.
2
How to see what ports are open on your computer? To do this, open a command prompt (console): "start" - "All programs" - "Accessories" - "Command prompt". In the black window (it can be customized) type netstat –aon and press Enter. Will list all current connections. In the first column indicates the type of network Protocol, TCP or UDP, in the second you will see the local address.
3
Pay attention to the figures walking in lines of the local address after the colon, this is the room open on your computer ports. How to know which program open it? To do this, note the last column – PID. This is the process ID. Knowing it, you can always check the name of the process to which it belongs. To do this in the same console window type the command tasklist. Displays a list of running processes on your computer. In the second column to find your ID on the left will be the name of the process.
4
There are times when you have to force to open in the firewall a port – that is to make it open to connect. When it comes to regular Windows firewall, then it is quite possible to work through the console. So, to open a port just type in the console the command netsh firewall add portopening TCP 45678 system and press Enter. This example will open a TCP port 45678.
5
To close the open port you must enter the CLI command: netsh firewall delete portopening TCP 45678. This example closes a previously opened port. You can watch the firewall settings by typing in the console etsh firewall show config.
6
Whether by means of firewall to forcefully close a specific port, that is to prevent programs to open it? You can, but that doesn't make any sense. Quality Trojans opened by them choose the port randomly, so it is impossible to guess which port should be closed to protect yourself from a Trojan.
7
To close all the "extra" ports is also impossible, since the Internet browser uses not only 80 port, but also others. So, first, you must configure the list of trusted applications, and secondly, look in the console the list of connections under suspicious network activity of the computer. Also in the firewall settings it is useful to turn logging connections.
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