Probably, you do not need to say that sometimes the user needs to use special ports in order to gain access, for example, to online games. Sometimes this is required by specialized Internet clients or complex specific programs. Let's try to figure out how to check if the ports in the system are open. As it turns out, this is not so difficult.
How to check if ports are open? Command line
So, let's start, perhaps, with the simplest that is only available to the user. As a rule, in most cases, the solution to the question of how to check whether ports are open on the system comes down to using the command line, the functional set of which is quite diverse and allows not only to view specific information, but also to correct many errors or malfunctions.
It is accessed by writing the cmd command to the Run menu bar, which, in turn, is called up either from the Start menu or by Win + R. In order to check whether the Windows port of interest to the user is open, First, you can display a complete list of ports, where the desired one will be present. To do this, use the netstat –a command. After its execution, a complete list of ports with their status will be displayed on the screen.
Using online resources
In some cases, the question of how to check whether the port used by any program or online game is open (especially if it is required to be accessible from the Internet) cannot be resolved without the help of special online resources. This is due only to the fact that the availability of a port has been checked, so to speak, from the outside - when trying to access the local machine, and not vice versa.
For such purposes, you can use a lot of sites that check the connection and status of the proposed open port. For example, you can use the Port-scanner section located on the WhatsMyIP.org resource as a quick scan tool. Here in the Custom Port Test section there is a special field in which the user needs to enter the port of interest to him, the field of which is to click the Start Test button. Needless to say, this process will take a little time. Upon completion, a result will be issued.
How to check if Telnet port is open in Windows XP
Finally, let's move on to checking open ports on remote computers. In Windows XP, as well as in any other system, this is done elementarily.
How do I check if the ports necessary to access certain Internet features or resources are open? Yes, as easy as shelling pears. Again, the command line will be used as the main tool . But this time it will be necessary to enter in it a variant of the Telnet command “server name” “port number” (for example, to check the connection via SMTP with port number 25 it looks like telnet smtp.name.ru 25, where the domain name is entered as the name ) As you can see, everything is simple.
Problems in Windows Vista and Above
Vista and higher may experience problems. This is due only to the fact that by default the Telnet service is simply disabled in them. Therefore, in order to check whether the ports of interest to a user are open, first it will have to be installed (activated).
In the simplest case, go to the programs and components section, and then check the box next to the Telnet client itself. If for some reason it doesn’t turn on, we use the following on the command line: dism / online / Enable-Feature / FeatureName: TelnetClient.
If the client is not in the list at all, go to the registry editor (regedit command in the "Run" menu) and then go down the HKLM / SYSTEM branch through the CurrentControlSet subfolder to the Windows directory. In the window on the right we find the CSDVersion parameter and instead of the value 200 we assign it to 0. Next, the same method is used as for the "export".
Why are some ports unavailable?
Based on the results, one can judge the state of a port. If at the moment one of them is unavailable, but you need to use it, there can be many reasons for this. Most often this is due to the effects of viruses. Sometimes you should check your TCP / IP settings. In some cases, you will have to verify that the settings of the router are correct, especially in the case of port forwarding on the router. You should also pay attention to the firewall settings - perhaps it is he who blocks the port. Finally, it is possible that the port is in the open state, and the time of its ping (response) is overestimated.
However, this is not about that now, since the correction of such errors and failures is a separate issue. As for the verification of the ports themselves, as can be seen from all of the above, it is done quite simply. Therefore, if, say, an unprepared user has such a problem, panic out of ignorance of the essence of the issue is not worth it. Any of the proposed solutions allows you to perform such operations in a matter of seconds. In general, it is obvious that when checking, for example, online, the user must know exactly which port he needs. But sometimes the problem may also be related to the fact that this port is blocked by the provider. Then you have to solve the problem at this level.