Open Port website is a free Open Port Check Tool to check a remote TCP port state – open or close. This tool can be also used to test your router or device for port forwarding.

Domain/IP: Port:

Please provide a Hostname and a port number to check. The defaults that you see are your IP address and the default Http port number 80:

Check other free online tools we have:

Some Well Known Ports

Port Number Description 21 FTP 22 SSH 23 Telnet 25 SMTP 53 DNS 80 HTTP 110 POP3 135 DCOM (but not only) 443 HTTPS 1433 MS SQL Server 1521 Oracle Listener 25565 MySQL

For a full list of port numbers refer to Wikipedia – List of TCP and UDP port numbers

Open Port Check Tool:

A port is a number that represents an entry to a service that is open to the network.

There are 65535 ports available to use. Some of the ports had been assigned to special service by INAN (Internet assigned numbers authority).

In computer networks, an open port is a port that currently uses (open) by a service. An open port can be used to send or/and receive data over the network.

There are two known types of ports. TCP ports and UDP ports. Open port check tool can check the state of a TCP port.

This can be done by sending a packet using the IPv4 (IP version 4) protocol.

An example can be your web browser on the client-side and a web server as the remote server.

The web server uses the default port 80 for HTTP or port 443 for HTTPS to listen and wait for connections.

Your browser establishes a connection to that port, using a local port. Once it connected they send and receive data between them.

An open port check tool can be used to check if the port is currently open or not on a target machine.

It is like a port test, using this tool you can also detect port forwarding status.

You can also use an open port check tool to remotely check if your server is being blocked by a firewall.

Port Scanner:

A port scanner is a tool that can be used to scan a range of ports.

A more advanced or port checker can scan some address or even a full network searching for ports that are open.

In computer security and hacking it is widely used to search for problematic open ports that suppose to be close or monitor.

An open port is like an open door or a window. With the right knowledge, it is possible to use this port to enter into the remote computer.

Using and running a regular port scan is a good method to find open ports and close them. If an open port is found it is also used to understand why and who open it.

There are some very useful tools that can be used to scan the network address for open ports. Using such tools can even find address inside the organization that needs to be removed.

An example of network ports scanner tool is Nmap. Using it you can scan full subnet. It supports several scan methods like TCP SYN scan and TCP ACK scan.

Advanced usage of the tool can detect what is the service (process) that open the port and the operating system behind this service.

Online port scanner:

The old art of port scanning is still working. Even thou that today there is a more secure method to close and monitor ports and services in the working environment.

For example. An Intrusion detection system (IDS) can be used to monitor the network.

With the advanced of new tools, an online port scanner tool can be used as a source to scan an environment. Scanning from outside the organization.

An online port scanner is a port scanner like any other port scanner. The only deferent is that it works from outside your network. re: a website – online.

It is a great tool that can be used to check if you have unnecessary open ports on your computer/device that needs to be closed.

Port forwarding:

Port forwarding allows devices from outside your network to connect to a specific device inside your private network. This is also known as port mapping.

This accomplishes by enabling port forwarding on your router and forward a connection to a special port. The port should be configured to pass the connection into a device in your LAN.

Firewall:

You also need to enable it on your windows firewall or the Unix IP table.

Firewall design for blocking and monitoring inbound and outbound traffic. Firewall monitoring the data against malicious activities.

In LAN (local area network) configuration the inner devices have an IP address that is only available inside the LAN. Most of the time it starts by 10.X or 192.X. The modem/router also has an external IP address that can get out to the internet.

This means that every device that uses the internet actually use the external IP address to surf the web.

The router/DSL modem know who request the external connection and forward the requested data to that device.

This is accomplished automatically by the router.

Once port forwarding is enabled, the device that is outside the LAN will be able to connect into the inner LAN.

This is done by assigning a port in the router or modem to forward state. Once done the incoming data forward to the relevant inner device on the desired port.

Did You Know:

To check a list of ports that currently open on your host and to see what are the IP addresses or the host that your computer is connected to, you can use the built-in command-line tool netstat it is one of the builds in network tools.

Other useful tools:

Have Fun.