# How to Check if a Port Is Open on a Remote Linux System or Server

> URL: https://www.atlantic.net/vps-hosting/how-to-check-open-port-on-a-remote-linux-system/ | Published: 2022-05-03 | Updated: 2024-06-01 | Author: Hitesh Jethva

A Port is a logical number assigned to a process running on Linux. The port can be defined as an integer number between **0** to **65535**. Ports with numbers **0–1023** are called system or well-known ports, while ports with numbers **49152-65535** are called dynamic, private, or ephemeral ports. If you are a Linux system administrator, you should know which ports are open and running on a remote system. There are several ways to find an open port on Linux.

This post will show the most reliable ways to find an open port on a remote Linux system.

## Find Open Port Using Netcat Command

Netcat is a Linux command-line utility that reads and writes data across network connections using TCP or UDP protocol. It also allows us to find open ports on a remote Linux system.

By default, the Netcat utility is not included in the Linux system. You will need to install it manually using the package manager.

For Ubuntu and Debian-based operating systems, install the Netcat utility using the following command:

```
apt-get install netcat -y
```

For RHEL, CentOS, Fedora, and Rocky Linux operating systems, install the Netcat utility using the following command:

```
dnf install nc -y
```

The basic syntax to use the Netcat command is shown below:

```
nc [-options] [host_name or ip] [port_number]
```

For example, to check if port **80** is open on the remote host **172.20.10.2**, run the following command:

```
nc -zv 172.20.10.2 80
```

If port 80 is open on a remote host, you will get the following output:

```
Connection to 172.20.10.2 80 port [tcp/http] succeeded!
```

**Where**:

- **-z** : Sets nc to scan for listening daemons.
- **-v** : Show output in verbose mode.

You can also specify a range of ports to be scanned:

```
nc -zv 172.20.10.2 40-80
```

The above command will scan for all ports between 40 and 80.

#### **Also Read**

[Netstat Command Line Tips and Tricks](https://www.atlantic.net/vps-hosting/netstat-command-line-tips-and-tricks/)

## Find Open Port Using Nmap Command

Nmap is a powerful and very popular command-line utility used to perform network-related tasks. By default, the Nmap utility is not included in the Linux system. You will need to install it manually using the package manager.

For Ubuntu and Debian-based operating systems, install the Nmap utility using the following command:

```
apt-get install namp -y
```

For RHEL, CentOS, Fedora, and Rocky Linux operating systems, install the Nmap utility using the following command:

```
dnf install nmap -y
```

The basic syntax to use the Nmap command is shown below:

```
nmap [-options] [HostName or IP] [-p] [PortNumber]
```

For example, to get a list of all open ports on a remote host **172.20.10.2**, run the following command:

```
nmap 172.20.10.2
```

You should see all open ports in the following output:

```
Starting Nmap 7.60 ( https://nmap.org ) at 2022-04-05 14:05 IST
Nmap scan report for vyompc (172.20.10.2)
Host is up (0.000078s latency).
Not shown: 996 closed ports
PORT     STATE SERVICE
22/tcp   open  ssh
23/tcp   open  telnet
80/tcp   open  http
7070/tcp open  realserver

Nmap done: 1 IP address (1 host up) scanned in 0.88 seconds
```

If you want to check if a particular port is open on the remote host, use the **-p** option:

```
nmap -Pn -p 80 172.20.10.2
```

You will get the following output:

```
Starting Nmap 7.60 ( https://nmap.org ) at 2022-04-05 14:08 IST
Nmap scan report for vyompc (172.20.10.2)
Host is up (0.00011s latency).

PORT   STATE SERVICE
80/tcp open  http

Nmap done: 1 IP address (1 host up) scanned in 0.04 seconds
```

## Find Open Port Using Telnet Command

[Telnet](https://www.atlantic.net/vps-hosting/how-to-install-and-use-telnet-on-debian/) is another network protocol used to virtually access a remote computer. It also allows you to find open ports on remote systems. You can install it manually using the package manager.

For Ubuntu and Debian-based operating systems, install the Telnet utility using the following command:

```
apt-get install telnet -y
```

For RHEL, CentOS, Fedora, and Rocky Linux operating systems, install the Telnet utility using the following command:

```
dnf install telnet -y
```

The basic syntax to use the Telnet command is shown below:

```
telnet [HostName or IP] [PortNumber]
```

For example, to check if port **22** is open on a remote host **172.20.10.2**, run the following command:

```
telnet 172.20.10.2 22
```

If port **22** is open, you will get the following output:

```
Trying 172.20.10.2...
Connected to 172.20.10.2.
Escape character is '^]'.
SSH-2.0-OpenSSH_7.6p1 Ubuntu-4ubuntu0.6
```

If port **22** is not open, you will get the following output:

```
Trying 172.20.10.2...
telnet: Unable to connect to remote host: Connection refused
```

## Conclusion

This guide shows how to find an open port on a remote machine using different commands. You can now choose your preferred tool to scan the remote system and find an open port. Try it on [VPS hosting](https://www.atlantic.net/vps-hosting/) from Atlantic.Net!