Website to check open ports

Today I was sitting in front of my laptop, thinking about what to write about. During my research, I found the following term, a website to check open ports, and thought about this website. Why not write an article about what this web site is doing, for free, so that everyone that looking for sites like this can find this site.

Website to check open ports:
Website to check open ports

Website to check open ports:

A website to check open ports is a service that lets you check if a port is open on not. If we are expending the port term. We can look at it as a door or a window into a hose. Where the house is a device, like a computer.

Every device, that connected to the internet has a unique identification, we call it IP Address. Think of it like your home address.

How an online open port tool is working?

An online open port check tool, in PHP for our discussion, is using a PHP code that tries to open a connection to the destination target on the selected port. If it manege to open the connection it means the remote port is open. If it does not manage to open a remote connection on the desired port. It means the port is open.

An advanced port checker may use other connectionless methods like SYN or others. When we establish a TCP connection there is a process name handshake. In this process, we send a package name SYN. The remote server reply with an SYN-ACK and then the client reply with an ACK to the server. This process got the handshake. In an advanced port checker, the client can send the SYN and wait for the SYN-ACK to know the port is open.

What is a port scanner?

Now that we know what is a port checker we can guess what is a port scanner. A port scanner will be able to check more than one port. It can scan a list of ports. Some port scanners can scan more than one target. It can also try to guess what is the target operating system based on the open port it finds, and a special packet it sends to them.

One of the best and known port scanner tool in nmap or network mapper. It has a lot of features, can detect the target operating system. It can be used to craft special packet for scanning and much more.

Internal port check tool:

The internal port check tool can check the port inside the organization network. For most of the internal port check a port scanner tool can be used. Using a tool like that can find hidden open ports within the network. It can run on a range of internal IP addresses to find the status of the internal ports.

Why using an external port checker?

External website to check open ports can be useful to check if our network is open from the outside, like the internet. It will show the list of open ports. This can be very valuable from a security perspective. Is there an open port that supposes to be close?

Another use of an external port checker is to check port forward. A port forward means that we configure the incoming connections for a specific port to be forward into the internal device or port. Using a website to check open ports we can verify that our port forward configuration was fine.

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