Paessler PRTG

All-in-one port monitoring software


  • icon check white 2
    PRTG monitors
    open and closed ports

  • icon check white 2
    PRTG monitors
    bandwidth & traffic

  • icon check white 2
    PRTG monitors connections
    using UDP and TCP protocols

  • icon check white 2
    PRTG includes SNMP,
    NetFlow, and packet sniffing







Port protocols 



A port is a part of the network address and ensures the proper distribution of connections and data packets. Valid port numbers range from 0 to 65535. Many applications use typical or standardized ports (“well-known ports”), which are usually registered with the IANA. These include FTP (port 20), SMTP (port 25), and SNMP (port 161). These ports are used primarily by protocols such as the Transmission Control Protocol (TCP) and User Datagram Protocol (UDP).

 Traffic Monitoring

Traffic monitoring

Many administrators search for port monitoring software to monitor the traffic that runs through their routers and switches, and the amount of bandwidth that is consumed. What they really need is network monitoring software. PRTG comes with a number of advantages: it is an all-in-one monitoring software and monitors the traffic on your devices with SNMP as a means of monitoring bandwidth, and it offers the technologies of flow protocols (including NetFlow, IPFIX, jFlow, and sFlow) and packet sniffing.



Open ports put your network at risk. They are used, for example, to introduce Trojans. While it is true that many administrators are highly security-oriented, it takes a superhuman effort to constantly check which ports are open and which are closed. Often ports are opened temporarily for individual applications and then forgotten. In such cases, PRTG checks if TCP/IP ports are open or closed and keeps administrators up-to-date by way of a built-in, customizable alarm system.


The right sensors for monitoring your ports and traffic

 i How PRTG defines sensors

In PRTG, “sensors” are the basic monitoring elements. One sensor usually monitors one measured value in your network, e.g. the traffic of a switch port, the CPU load of a server, the free space of a disk drive. On average you need about 5-10 sensors per device or one sensor per switch port.

View video (3:26 min.)

  • SNMP Traffic Sensor: This sensor monitors data traffic on your routers and switches.
  • Packet Sniffer Sensor: This sensor monitors data packets according to types of traffic (mail, FTP, Citrix, chat, etc.).
  • NetFlow v9 Sensor: With this sensor, you can monitor your Cisco hardware using NetFlow technology. Also available in V5 or IPFIX.
  • NetFlow v5 Sensor: This sensor receives traffic data from a NetFlow v5 compatible device and shows the traffic by type.
  • sFlow Sensor: This sensor only analyzes header traffic and has serveral filter options available to divide traffic into different channels.
  • jFlow v5 Sensor: This sensor monitors data traffic according to types by analyzing the header traffic.
  • IPFIX Sensor: This sensor receives traffic data from an IPFIX compatible device and offers several filter options to divide traffic into different channels.


  • Port Sensor: This sensor monitors a network application by connecting to the respective TCP/IP port. It can also perform Telnet commands.
  • Port Range Sensor: This sensor monitors a range of ports and indicates whether these ports are open or closed.
  • Discover 250 more sensors in our sensor list. Our free trial version comes with the full selection of PRTG sensors. You can use this version to try all PRTG features.

A quick introduction to PRTG: Port monitor


Port Monitoring: 5 reasons why PRTG is the right tool for you

 i NetFlow is a protocol for collecting, aggregating and recording traffic flow data in a network. NetFlow data provide a more granular view of how bandwidth and network traffic are being used than other monitoring solutions, such as SNMP. NetFlow was developed by Cisco and is embedded in Cisco’s IOS software on the company’s routers and switches and has been supported on almost all Cisco devices since the 11.1 train of Cisco IOS Software.
Read more

 All in one

All in one

Whether SNMP, packet sniffing, or NetFlow: All standard monitoring protocols are included. The notification system is also part of the overall package. Get started with a central monitoring tool that works on your entire network – and finally enjoy some peace of mind as you concentrate on your other tasks. Many administrators use PRTG because they wish to do away with their “hodgepodge” of monitoring tools. 



For nearly 20 years, Paessler AG has been fully dedicated to the development of its PRTG monitoring software in order to offer the perfect network monitoring tool. Today, more than 500,000 administrators worldwide put their trust in our monitoring software for the monitoring of their networks and traffic.



PRTG comes with extensive support. We aim to resolve every support inquiry within 24 hours (on business days). Our knowledge base contains a number of concrete application tips. You will find answers to many of your questions there. Our manual also contains instructions for every sensor.



PRTG lets you create your own customized reports. Thanks to these reports, you can study the evolution of bandwidth, system load, and many other parameters over the course of months or years. This will help you with the long-term planning of your network infrastructure. You can also detect load peaks and react to them quickly.



PRTG comes with a built-in notification system. This alarm is entirely customizable. You will only receive a notification if an error occurs. At the same time, the alarm can be configured in such a way as to provide prompt alerts – before larger problems or system failures arise.


Decision time: Individual port monitoring software or an all-in-one monitoring solution?

Isolated applications

While searching for port monitoring software, you are bound to stumble across a number of isolated software applications such as CurrPorts or Port Scan. In the short term, such solutions are perhaps not all that bad. However, they tend to make monitoring complex and confusing. Those opting for several isolated applications have to live with higher maintenance costs and often limited features. Therefore, it is extremely difficult to keep a constant eye on your network.

Advantages of PRTG

With PRTG, you get one central monitoring tool for your entire network. The trial version is free of charge, including all its sensors and functions. You will thus gain a complimentary and risk-free glimpse into our software, and can even set up port monitoring and collect some initial data. Upgrade whenever you like.


quote john krull

“Our network engineers really love PRTG, because of its customization”

John Krull, CTO, Oakland Unified School District, USA


Trusted by 500,000 users and recognized
by industry analysts as a leader

“Fantastic network and infrastructure monitoring solution that is easy to deploy and easier still to use. Simply the best available.”

Read more reviews

“Software is absolutely perfect, Support is superior. Meets all needs and requirements, this is a must have solution if you are needing any form of monitoring.”

Read more reviews

“The tool excels at its primary focus of being a unified infrastructure management and network monitoring service.”

Read more reviews


Port sniffer vs. port monitoring

Port sniffer

A port sniffer sniffs network traffic in detail, i.e. tracks it or records it. The question here is how deep the system administrator wants to go. Those who want to see the content of individual packets, need specialized software such as Wireshark. With PRTG as a port scanner, you have the option using our Packet Sniffer sensor to identify traffic on the packet level. However, you will not see concrete content, but protocols, IP addresses and connections.

Port monitoring

Port monitoring means long-term monitoring of the ports in their network. PRTG is helpful here. If a disruption or problem occurs, you will receive a notification. This helps you in day-to-day work and also makes it easier to perform a fast analysis and troubleshoot in case of problems. Port monitoring is often also part of a security architecture of an IT system.


TCP and UDP: That is the difference


TCP is the most commonly used protocol to send packets. It guarantees that the data are received correctly, because the packets are numbered consecutively. The recipient sends a response that the data arrived. Otherwise, the TCP packet is sent another time. This is how TCP ensures with high certainty that all packets arrived. However, the resulting load is higher than in UDP. There are standardized ports for TCP.


UDP is a connectionless protocol. There is no sequential numbering or check. It generates much less load. Therefore, UDP is more economical, but also more prone to errors. The UDP protocol is often used for applications where packet loss is not so important. There are also standardized ports for UDP.

TCP/UDP monitoring tool

With PRTG, you monitor IP packets and can also filter by TCP and UDP packets. This way, you can identify packet delays or losses immediately, along with their impact on quality of service. In addition, you can monitor the connectivity of TCP ports and their response to certain commands.


Port mirroring and PRTG


"Port mirroring" (also "monitoring port") is used in PRTG for packet sniffing and must offer the switch or router to be monitored. It sends a copy of all data packets going through to the "monitoring port", enabling packet sniffing. For this, the PRTG probe must only be connected to the port via the network card.


daniel elsner

"Hey Daniel, do you have any port monitoring tips up your sleeve?"

"With routers, switches, hubs, and bridges, your network has a great deal of ports which potentially need to be monitored. I would therefore recommend creating at least one active sensor per port on each of your central network components. By doing so, you should be able to monitor all of a network device’s active ports, as well as its CPU and RAM. On the other hand, for those network components which are not so vital, it is often sufficient to use paused sensors instead of actively monitoring every port."

Daniel Elsner, PRTG Product Development


Hardware ports that you should keep an eye on

Switch ports

Switch ports

Switches are typically bottlenecks in a network. The failure of a single switch can impact an entire network. With switch port monitoring, you can see anytime whether and how much traffic runs through your switch. By the way, for all big manufacturers, the monitoring of Cisco switches is included with us. More about switch monitoring.

Router ports

Router ports

How many router ports are currently in use and how many are still free? Which router ports reached their capacity? With continuous router port monitoring, you can identify early on when ports reach their capacity. The regular port scan helps you with capacity planning.

Server ports

Server ports

Servers are the heart of any IT infrastructure. If there are disruptions at the server port, this can usually be felt immediately in the whole network. With PRTG, you monitor your servers and also your server ports.



Which ports does PRTG use?

PRTG needs certain ports to function properly. As an administrator, you will have to free up these ports. Here you will find an initial overview.

You can also find out more in our Knowledge base article: „Which ports do I need for PRTG?"

  • Web server: The web server requires TCP ports 80 (HTTP) and 443 (HTTPS), and uses fallback ports 8443, 32000+ (HTTPS), and 8080 (HTTP).
  • Reports: Have reports sent as PDF files. For this, port 8085 is required.
  • Auto-Update and Activation: Port 443 is required for Auto-Update and Activation
  • Update Check und Download: Port 80 is required for Update Check and Download.
  • Active Directory Integration: Here, ports 389 (TCP and UDP) and TCP 636 (SSL-secured) are used.
  • Remote Probes: Port 23560 is required for the connection between remote probes and the core server.
  • Cluster: Communication amongst cluster nodes takes place via port 23570.
  • PRTG Cloud: TCP port 443 is used to access the PRTG Cloud (e.g. for push notifications and the Cloud Ping and Cloud HTTP sensors).
  • SNMP: For SNMP, UDP port 161 is used.

Create innovative solutions with Paessler’s IT partners

Partnering with innovative IT vendors, Paessler unleashes synergies to create
new and additional benefits for joined customers.

IP Fabric

Combining the broad monitoring feature set of PRTG with IP Fabric’s automated network assurance creates a new level of network visibility and reliability.

Read more


Rhebo and PRTG offer a comprehensive monitoring solution for IT and OT environments: from condition monitoring through to anomaly and threat detection.

Read more


“Easy to implement and configure with good technical support.”

R. v. S., ICT Manager at Heinen & Hopman Eng BV


PRTG makes your job easier

Our monitoring software frees you to focus on other tasks by promptly notifying you of potential issues.


time white

Save effort

PRTG gives you one central monitoring tool for your servers and entire network. Enjoy a quick overview of your whole infrastructure via our dashboard and app.

brain white

Save time

Getting started with PRTG is a breeze. Setting up or switching from another network monitoring tool is easy thanks to the auto-discovery and pre-configured device templates.

money white

Save money

80% of our customers report substantial cost savings with network monitoring. Your costs of licenses will likely pay for themselves within weeks.



PRTG the multi-tool

PRTG: The multi-tool for sysadmins

Adapt PRTG individually and dynamically to your needs and rely on a strong API:

  • HTTP API: Access monitoring data and manipulate monitoring objects via HTTP requests
  • Custom sensors: Create your own PRTG sensors for customized monitoring
  • Custom notifications: Create your own notifications and send action triggers to external systems
  • REST Custom sensor: Monitor almost everything that provides data in XML or JSON format


You want to know more about other network-related monitoring topics?


How can I measure my bandwidth? How can PRTG help in difficult situations? How can I use PRTG to test my bandwidth? Find the answers to these and many more questions.

Learn more


The concept of sensors is a central part of PRTG. In our four-minute video, you will get a basic idea of how sensors work and how best to use them.

Learn more

LAN Monitoring

Whether LAN, WAN, or distributed networks: With PRTG, you get a constant overview of your entire network. The LAN Monitoring page provides information on the five pillars upon which this monitoring rests.

Learn more

NTP Monitoring

The NTP Sensor continuously compares the times of your network devices with the times of a precise NTP server. This allows all network log files to be compared with one another.

Learn more

IPv6 Cheat Sheet

You want to know everything about IPv6?

You probably have been working with IPv4 for years. But what about IPv6? In our cheat sheet you get all the details about the IPv6 header, the correct address allocation, typical ICMPv6 error messages and much more.

Get your free copy of our IPv6 cheat sheet now.


Still not convinced?



More than 500,000 sysadmins love PRTG

Paessler PRTG is used by companies of all sizes. Sysadmins love PRTG because it makes their job a whole lot easier.

Still not convinced?


Monitor your entire IT infrastructure

Bandwidth, servers, virtual environments, websites, VoIP services – PRTG keeps an eye on your entire network.



Try Paessler PRTG for free

Everyone has different monitoring needs. That’s why we let you try PRTG for free. Start now with your trial.




Network Monitoring Software - Version (October 2nd, 2023)


Download for Windows and cloud-based version PRTG Hosted Monitor available


English, German, Spanish, French, Portuguese, Dutch, Russian, Japanese, and Simplified Chinese


Up to 100 sensors for free (Price List)

Unified Monitoring

Network devices, bandwidth, servers, applications, virtual environments, remote systems, IoT, and more

Supported Vendors & Applications

cisco logo grey 40 dell logo grey 40 hp logo grey 40 ibm grey40 netapp grey40 linux grey40 aws grey40 windows grey40 vmware grey40 citrix grey40 exchange grey40 apache grey40 oracle grey40