There'south a good chance you've happened upon this article considering an application y'all're trying to run is lament about a "port" being blocked or you've read almost how leaving certain "ports" open on your network tin be a security trouble.

Either fashion, by the end of this piece yous'll not only know what these ports everyone is going on about are, but how to bank check your computer to find open or closed ports.

What Is a Network Port?

The kickoff thing you should know is that the ports we're referring to here are virtual. It has nothing to practice with the physical network hardware ports on your router, TV, consoles or computers. Ports are simply a manner for your network hardware and software to organize data traffic.

Think of reserved lanes on a route. The sidewalk is for pedestrians. There might exist a dedicated bike lane. Carpool vehicles and buses have their own lanes too. Ports serve the same function. Ane port might be used for receiving emails, while another carries file transfer requests, or website traffic.

There are two common types of ports, which need a brief explanation earlier we move on to checking which ports on your system are open and which aren't.

What Are TCP & UDP Ports?

The ii common types of ports on modern networks are known every bit TCP and UDP ports. That is Transmission Control Protocol and User Datagram Protocol respectively. So these ii port types utilize unlike network protocols.

Which y'all can think of equally distinctive sets of rules for how bits of data should be sent and received. Both port types are built on the fundamental Internet Protocol (IP) that makes the internet and home networks, well, work. Withal, they are suitable for dissimilar applications.

The big difference is that when y'all send information over UDP, the sender doesn't starting time have to institute a connection with the receiver before starting the conversation. It's a chip like sending a letter. You don't know if the other person received your message and you accept no guarantee that you'll get any feedback.

TCP, on the other hand, is more than similar making a phone call. The receiver has to "pick upwards" the connection and there'due south a back-and-along flow of information until someone deliberately hangs up.

UDP messages are mostly circulate over a network to anyone who is listening on the specified UDP port. This makes it perfect for housekeeping type messages that relate to running the network itself. It's also perfect for voice-over-IP streaming, online video games and streaming broadcasts.

Why? These applications benefit from UDP's low latency and constant stream of information that doesn't have to be perfect to be useful. A little corruption in your Skype conversation is far less important than low amounts of lag, after all.

TCP is much more common than UDP and absolutely makes sure that all data is received free from errors. But about everything that doesn't demand the specific advantages of UDP, uses TCP instead.

Which Ports Are Usually Open By Default?

There are a LOT of ports. A port number can be anything from 0 to 65535! That doesn't mean any application can just pick whatsoever port. There are established standards and ranges, which helps us brand sense of the dissonance.

Ports 0-1023 are associated with some of the most important and key network services. This makes sense, since the lower-numbered ports were assigned first. The SMTP protocol for email, for case, is exclusively used past port 25.

Ports 1024-49151 are known as "registered ports" and are assigned to important common services such as OpenVPN on port 1194 or Microsoft SQL on ports 1433 and 1434.

The rest of the port numbers are known as "dynamic" or "individual" ports. These ports aren't reserved and anyone can apply them on a network to support a particular service. The only problem crops upward when ii or more services on the same network are using the same port.

While it's impossible to list every single important port, these common ports are useful to know by middle:

  • xx – FTP (File Transfer Protocol)
  • 22 – Secure Shell (SSH)
  • 25 – Simple Mail Transfer Protocol (SMTP)
  • 53 –  Domain Proper name System (DNS)
  • 80 – Hypertext Transfer Protocol (HTTP)
  • 110 – Post Role Protocol (POP3)
  • 143 – Internet Message Access Protocol (IMAP)
  • 443 –  HTTP Secure (HTTPS)

Since in that location are and then many thousands of common port numbers, the easiest approach is to remember the ranges. Which volition tell you if a given port is reserved or not. Thanks to Google, you tin can too look up which services use a specific port in no time at all.

Find Open Ports In Windows

Now that we've got all the basic knowledge about TCP and UDP ports out of the fashion, it'south time to get down to the process of finding which ports are open up and in use on your computer.

The expert news is that Windows has a pretty useful control built into it that will show you what ports are currently being used on your computer by various applications and services.

  • The first thing you want to do is open up the Start Menu and search for CMD.
  • Now, right-click on CMD and Run as Administrator.
  • With the Control Prompt open, type:

Netstat -ab

  • Don't worry near a long listing of info scrolling by faster than you can read information technology. You tin simply use CTRL+C and CTRL+Five to re-create and paste the information into Notepad or any other text editor.
  • The information in brackets is the proper name of the program that's using the port. TCP or UDP refers to the protocol being used on that port. The number consists of an IP accost and then the port number after the colon.

Scanning For Blocked Ports

That takes care of finding which ports are beingness used and past which application, but information technology doesn't tell u.s. which ports are being actively blocked by the Windows Firewall.

  • Once over again, open up the Start Bill of fare and search for CMD.
  • Right-click on CMD and Run every bit Ambassador.
  • With the Command Prompt open, type:

netsh firewall show land

This is a display of blocked and open ports every bit per the configuration of your Windows Firewall.

You'll see a note about this command existence deprecated, simply the new command doesn't testify u.s. the information we want. So for now using the 'show country' command is still the fastest and easiest manner to get port information.

Merely because the Windows Firewall isn't blocking a port, that doesn't hateful your router or Internet access provider aren't. Then the last affair we desire to do is bank check if any external blocking is happening.

  • Open the Start Carte and search for CMD.
  • At present, right-click on CMD and Run as Ambassador.
  • With the Command Prompt open, type:

netstat -ano | findstr -i SYN_SENT

If you don't get whatsoever hits listed, then nix is being blocked. If some ports are listed, it means they are beingness blocked. If a port not blocked by Windows shows up hither, you lot may desire to check your router or popular an electronic mail to your ISP, if switching to a unlike port isn't an selection.

Useful Apps To Map Out Your Port Status

While the Command Prompt is a good quick and dirty tool, there are more refined third-party applications that can help you become a motion-picture show of your port configuration. The 2 highlighted here are merely popular examples.

SolarWinds Costless Port Scanner

SolarWinds requires that you submit your name and details in lodge to download it, but it's up to you whether you put your real information into the form or not. We tried several free tools earlier settling on SolarWinds, just it was the only tool that both worked properly under Windows 10 and had an easy interface.

It was also the only 1 non to trigger a simulated positive virus flag. One of the big issues with port scanning software is that security companies tend to see them as malware. So most users ignore any virus warning that come up with such tools. That's a problem because you tin't tell the difference between a false positive and a existent virus in these apps.

SolarWinds might come up with some strings attached, but information technology really works as advertised and is easy to utilize.

CanYouSeeMe

This is, as y'all can probably tell, a website service rather than an application. It'south a good offset port of call to meet if external data can get through your local port or non. It auto-detects your IP address and all you have to do is specify which port to test.

It will then tell you if the port is blocked or not and you lot'll then have to figure out whether the blockage is on the computer, router or at the service provider level.

Conclusion

For well-nigh users, ports aren't something you lot need to worry about. They are managed by your operating organization, applications and network hardware.

When things go wrong however, it'south good to have the tool in manus that let you find open ports to sniff out suspicious action or effigy out where exactly your precious information is hitting a brick wall.