The following sensor types allow to monitor various TCP and UDP based services:

  • PING: Performs one or more PINGs to monitor the availability of a device and optionally measure packet loss in percent.
  • PORT: Checks the availability of TCP based network services.
  • FTP: Monitors the availability of a FTP Server.
  • DNS: Checks a DNS (Domain Name Service) server.
  • RDP (Remote Desktop): Checks whether the RDP service of a device is available.
  • HDD Health: Monitors the health of IDE disk drives via "SMART".
  • RADIUS: Checks "Remote Authentication Dial In User Service" servers. It connects to a RADIUS server and checks if login credentials are accepted.
  • Syslog Receiver: Receives and analyzes Syslog messages (can only be used in probe devices).
  • SNMP Trap Receiver: Receives and analyzes SNMP Traps (can only be used in probe devices).

FTP Sensor

FTP (short for File Transfer Protocol) is used on the Internet for exchanging files (e.g. to upload content to a webpage or to download files from a server). The FTP sensor monitors a FTP server's availability.

Parameters include:

  • Timeout: If the reply takes longer than this value the request is aborted and an error state is triggered.
  • Port: The port number of the FTP service you want to monitor (usually port 21).
  • FTP Mode: If you don't get a connection, use the passive mode.
  • Username: The FTP username to log in with.
  • Password: The FTP password for this username.
  • TLS (Transport-Level Security): Select whether or not to use a secure connection. If you chose "Use", you can additionally select an SSL-Method. If you do not get a connection, try a different SSL method.

DNS Sensor Configuration

The DNS (Domain Name System or Service) is an Internet service that translates domain names (which are easier for humans to remember) into IP addresses (which computer use to address each other). Every time you use a domain name, therefore, a DNS service must translate the name into the corresponding IP address. For example, the domain name www.paessler.com might translate to 62.146.51.168.

The DNS sensor sends a request to resolve a specific domain name to an IP address to the server it is associated with. This is useful e.g. to ensure that a company's web server address can be resolved by the outside world or to check a DNS server in a LAN for availability.

Note: The device associated with this sensor has to be a DNS server and not the domain name of the server you want to monitor. As DNS server, the sensor will use the IP-Address/DNS Name of the device you're creating this sensor on.

If you only enter the Domain in the settings, PRTG will only check whether the name is resolved to an IP address at all (which simply means that the DNS server works correctly and the domain name is valid). If you also enter an IP address the resolved IP address will be compared to this and the sensor will show an error when the two addresses are different.

DNS Specific parameters include:

  • Timeout: If the reply takes longer than this value the request is aborted and an error message is triggered.
  • Port: Define the DNS port.
  • Domain: Enter the domain name to look up (e.g. www.yourcompany.com).
  • IP Address: Optionally enter an IP address to compare the result with.


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