How to open port 4000?

• Navigate to Control Panel, System and Security and Windows Firewall.
• Select Advanced settings and highlight Inbound Rules in the left pane.
• Right click Inbound Rules and select New Rule.
• Add the port you need to open and click Next.

Need to connect to an outside PC or server—or need another PC or server to connect to you? If you’re running Linux, you’ll need to make sure the right port is open.

While other operating systems usually have some graphical tool for this, Linux isn’t so simple. We’ll walk you through how to open ports in Linux below.

A port is an end point on the network. Think of it like a door that leads to a particular room or the outside world, but on your computer. Everything you do on the internet uses a particular port or series of ports.

For example, let’s say you want to run your own Minecraft server. To do so, you’ll need to open a port for users to connect to it through. The same would apply to running your own web, mail, or FTP server.

Ports are standardized across all network-connected devices. The first 1,024 ports (from 0 to 1023) are referred to as well-known port numbers. They are reserved for the most commonly used services, such as HTTP and HTTP (port 80 and 443, respectively) and SSH (port 22).

Port numbers above 1024 are referred to as ephemeral ports, and are typically available for you to use for your online gaming, private web servers, and so forth. Port numbers 1024 to 49151 are called registered or user ports, while those from 49152 to 65535 are known as dynamic or private ports.

Before you start trying to open a port on Linux, you should make sure it isn’t already in use. You can accomplish this using the netstat command, included on most Linux distributions. If your distribution doesn’t have netstat, you can use ss instead.

This will print all listening sockets (-l), along with the port number (-n). It includes TCP ports (-t) as well as UDP (-u). If your system doesn’t have netstat, just use ss with the same parameters.

For the sake of this example, we’ll assume we want to open port 4000 to TCP connections. We first need to make sure the port isn’t already in use. We do this through netstat or ss.

Assuming the output is blank, we can add the appropriate port rules to the system’s firewall. Methods for this will vary depending on your distribution and whether it uses the newer ufw firewall or firewalld. Ubuntu favors ufw, while CentOS typically uses firewalld instead. Of course, there are still some Linux distributions using the older iptables firewall.

Rather than using the older iptables firewall, Ubuntu and some other distributions use ufw. Under these systems, the following command will open the port.

Skip past the next few steps, and test your newly-opened port to make sure it’s working.

If your system uses firewalld, your best bet is to use the firewall-cmd command to update the rules.

This won’t be a permanent change, but we’ll cover how to make the rules persist after rebooting once we test the port.

If your Linux system doesn’t have ufw or firewalld, you’ll need to use iptables. If it’s not installed, go ahead and get it using your package manager of choice. Once it’s installed, this commands will open port 4000:

If your system uses systemctl, replace the second command with:

Next, we should test the port to make sure it accepts connections. We do this by using netcat (nc) to listen to the port, then attempting to telnet to it.

First, open a terminal window and issue this command:

Leave it running (listening) and open a second terminal window. In that window, you’ll use telnet to test connectivity. If telnet isn’t installed, do so using your package manager.

Replace with your system’s IP address, and with the port number you opened.

You should see output like that below, indicating an open connection with nc.

We can also show the port is open using nmap. Again, if the command isn’t installed already, use your package manager to retrieve it.

Note that nmap will only list open ports that are listening for connections. That’s why we use netcat for testing, to listen on that port. Otherwise, the port won’t register as being open.

If you run through all of the steps above and can’t achieve a connection to the port, double-check your typing. If you’re certain you entered everything correctly, chances are you’ll need to reconfigure your network router to allow the traffic.

Since every network router has different configuration screens, you should consult the support pages or user’s manual for your particular equipment. You’ll need to check for port forwarding or port mapping settings, as well as any built-in firewall the router may use.

Once you’ve tested your open port and made sure it’s working, you’ll probably want to make the change permanent. Otherwise, the changes may not stick around after a reboot. If you’re an Ubuntu user, or otherwise use the ufw firewall, you don’t have to worry about this. The ufw rules don’t reset on reboot.

Making a port rule stick around after a reboot is easy with firewalld. Just add the —permanent flag to your initial command, and it will be included in your Linux system’s firewall rules on startup.

The iptables firewall is much more troublesome (maybe a good reason to upgrade to firewalld or ufw). To “permanently” open a port in iptables, you can install the iptables-persistent package to help.

When you first install iptables-persistent on a Debian-based system, it will save your current rules to either /etc/iptables/rules.v4 or /etc/iptables/rules.v6. To add new rules, you’ll issue the following command:

OR

For those running RPM-based Linux distributions, it’s a bit different. The package is called iptables-services, and the save files are /etc/sysconfig/iptables and /etc/sysconfig/ip6tables.

On RPM-based distributions, there is also a different command used for IPv6 ports. Saving your rules is done using one of these two commands:

As time goes on, your server needs may change. Just as you should keep abreast of the user accounts on your Linux machine, you should also audit your open ports regularly. Close any open ports no longer needed. Along with regularly changing your password, this is a good security practice that will help you avoid system intrusions and security exploits.

A port is a communication endpoint. Within an operating system, a port is opened or closed to data packets for specific processes or network services.

Typically, ports identify a specific network service assigned to them. This can be changed by manually configuring the service to use a different port, but in general, the defaults can be used.

The first 1024 ports (port numbers 0 to 1023) are referred to as well-known port numbers and are reserved for the most commonly used services. These include SSH (port 22), HTTP (port 80), HTTPS (port 443).

Port numbers above 1024 are referred to as ephemeral ports.

In this tutorial, you will open an ephemeral port on Linux, since the most common services use the well-known ports.

To complete this tutorial, you will need:

Before opening a port on Linux, you must check the list of all open ports, and choose an ephemeral port to open that is not on that list.

Use the netstat command to list all open ports, including TCP and UDP, which are the most common protocols for packet transmission in the network layer.

This will print:

Verify that you are receiving consistent outputs using the ss command to list listening sockets with an open port:

This will print:

This gives more or less the same open ports as netstat.

Now, open a closed port and make it listen for TCP connections.

For the purposes of this tutorial, you will be opening port 4000. However, if that port is not open in your system, feel free to choose another closed port. Just make sure that it’s greater than 1023.

Ensure that port 4000 is not used using the netstat command:

Or the ss command:

The output must remain blank, thus verifying that it is not currently used, so that you can add the port rules manually to the system iptables firewall.

Use ufw - the command line client for the UncomplicatedFirewall.

Your commands will resemble:

Refer to How to Setup a ufw Firewall Setup for your distribution.

Use firewall-cmd - the command line client for the firewalld daemon.

Your commands will resemble:

Refer to How to Set Up firewalld for your distribution.

Use iptables to change the system IPv4 packet filter rules.

Refer to How To Set Up A Firewall Using iptables for your distribution.

Now that you have successfully opened a new TCP port, it is time to test it.

First, start netcat (nc) and listen (-l) on port (-p) 4000, while sending the output of ls to any connected client:

Now, after a client has opened a TCP connection on port 4000, they will receive the output of ls. Leave this session alone for now.

Open another terminal session on the same machine.

Since you opened a TCP port, use telnet to check for TCP Connectivity. If the command doesn’t exist, install it using your package manager.

Input your server IP and the port number (4000 in this example) and run this command:

This command tries to open a TCP connection on localhost on port 4000.

You’ll get an output similar to this, indicating that a connection has been established with the listening program (nc):

The output of ls (while.sh, in this example) has also been sent to the client, indicating a successful TCP Connection.

Use nmap to check if the port (-p) is open:

This command will check the open port:

The port has been opened. You have successfully opened a new port on your Linux system.

But this is only temporary, as the changes will be reset every time you reboot the system.

The approach presented in this article will only temporarily update the firewall rules until the system shuts down or reboots. So similar steps must be repeated to open the same port again after a restart.

ufw rules do not reset on reboot. This is because it is integrated into the boot process, and the kernel saves the firewall rules using ufw by applying appropriate config files.

You will need to apply the --permanent flag.

Refer to How to Set Up firewalld for your distribution.

You will need to save the configuration rules. These tutorials recommend iptables-persistent.

Refer to How To Set Up a Firewall Using iptables for your distribution.

If you’re looking for a simple solution for opening firewall ports in Windows 10, you’ll find all the necessary details in this article.

Opening Firewall ports allow apps and programs to communicate with the network. So, if some of your apps and programs fail to launch, opening firewall ports is one of the first troubleshooting solutions that you can use.

Users can manually allow a program to get access to the Internet by opening a firewall port. All you need to know is what port it uses and the protocol to make this function.

1. Navigate to Control Panel> System and Security > Windows Firewall.

2. Go to Advanced settings.

3. Right-click on Inbound Rules > select New Rule.

4. Add the port you want to open and then click Next.

5. Choose the TCP or UDP protocol and the port number, then click Next.

6. Select Allow the connection and then hit Next.

7. Choose the network type, then click Next.

8. Name the rule and press on Finish afterwards.

These are all the necessary steps for opening a port in Windows 10. Remember that you can also use this method for blocking programs or ports.

Firewalls are targeted at protecting your network from various threats coming from outside and trying to get in or threats coming from inside trying to get out. A threat does this by blocking network-enabled ports.

Every time a program tries to communicate through this port, the firewall verifies its database rules to check if it is allowed or not. If it doesn’t know, it will ask the user and that’s why you sometimes see a prompt asking you if a certain program is allowed or not to access the Internet.

A firewall is an essential issue regarding computing and every PC must have one installed. This is the reason why Windows has a firewall bundled and active as standard.

Check out our articles on the best firewalls and the best network security antiviruses to use on Windows for more information.

Windows firewalls must occasionally be told to allow a program to communicate with the network and this is the point where opening ports step into the picture.

We hope that our article helped you open ports on Windows 10 devices. Let us know in the comments section below if you have any questions.

A port is a communication endpoint. Within an operating system, a port is opened or closed to data packets for specific processes or network services.

Typically, ports identify a specific network service assigned to them. This can be changed by manually configuring the service to use a different port, but in general, the defaults can be used.

The first 1024 ports (port numbers 0 to 1023) are referred to as well-known port numbers and are reserved for the most commonly used services. These include SSH (port 22), HTTP (port 80), HTTPS (port 443).

Port numbers above 1024 are referred to as ephemeral ports.

In this tutorial, you will open an ephemeral port on Linux, since the most common services use the well-known ports.

To complete this tutorial, you will need:

Before opening a port on Linux, you must check the list of all open ports, and choose an ephemeral port to open that is not on that list.

Use the netstat command to list all open ports, including TCP and UDP, which are the most common protocols for packet transmission in the network layer.

This will print:

Verify that you are receiving consistent outputs using the ss command to list listening sockets with an open port:

This will print:

This gives more or less the same open ports as netstat.

Now, open a closed port and make it listen for TCP connections.

For the purposes of this tutorial, you will be opening port 4000. However, if that port is not open in your system, feel free to choose another closed port. Just make sure that it’s greater than 1023.

Ensure that port 4000 is not used using the netstat command:

Or the ss command:

The output must remain blank, thus verifying that it is not currently used, so that you can add the port rules manually to the system iptables firewall.

Use ufw - the command line client for the UncomplicatedFirewall.

Your commands will resemble:

Refer to How to Setup a ufw Firewall Setup for your distribution.

Use firewall-cmd - the command line client for the firewalld daemon.

Your commands will resemble:

Refer to How to Set Up firewalld for your distribution.

Use iptables to change the system IPv4 packet filter rules.

Refer to How To Set Up A Firewall Using iptables for your distribution.

Now that you have successfully opened a new TCP port, it is time to test it.

First, start netcat (nc) and listen (-l) on port (-p) 4000, while sending the output of ls to any connected client:

Now, after a client has opened a TCP connection on port 4000, they will receive the output of ls. Leave this session alone for now.

Open another terminal session on the same machine.

Since you opened a TCP port, use telnet to check for TCP Connectivity. If the command doesn’t exist, install it using your package manager.

Input your server IP and the port number (4000 in this example) and run this command:

This command tries to open a TCP connection on localhost on port 4000.

You’ll get an output similar to this, indicating that a connection has been established with the listening program (nc):

The output of ls (while.sh, in this example) has also been sent to the client, indicating a successful TCP Connection.

Use nmap to check if the port (-p) is open:

This command will check the open port:

The port has been opened. You have successfully opened a new port on your Linux system.

But this is only temporary, as the changes will be reset every time you reboot the system.

The approach presented in this article will only temporarily update the firewall rules until the system shuts down or reboots. So similar steps must be repeated to open the same port again after a restart.

ufw rules do not reset on reboot. This is because it is integrated into the boot process, and the kernel saves the firewall rules using ufw by applying appropriate config files.

You will need to apply the --permanent flag.

Refer to How to Set Up firewalld for your distribution.

You will need to save the configuration rules. These tutorials recommend iptables-persistent.

Refer to How To Set Up a Firewall Using iptables for your distribution.

In this tutorial, you learned how to open a new port on Linux and set it up for incoming connections. You also used netstat, ss, telnet, nc, and nmap.