- Answer only the networks that need the service (no open resolvers, relays or reflectors).
- UDP services can be abused for DDoS amplification: rate-limit or block them at the edge.
- Disable legacy test services that have no use in production.
Port 6900: R*TIME Viewer Data Interface
Port 6900 is assigned by IANA to rtimeviewer (R*TIME Viewer Data Interface).
6900
How rtimeviewer works
Network servicesThe client sends a request to port 6900 and the rtimeviewer service answers.
- Transport
- TCP
- Exposure risk
- not rated depends on the program listening
- Encryption
- Unknownnot stated by the registry
- IANA status
- Assigned1 registered service
- Range
- Registered (1024-49151)
- Category
- Network services
Is port 6900 dangerous?
We have no specific security note for port 6900. Its risk depends on the program actually listening on it. General advice for network services services:
IANA registry entries for port 6900
| Service | Port | Transport | Description | Reference | Updated |
|---|---|---|---|---|---|
| rtimeviewer | 6900 | TCP | R*TIME Viewer Data Interface | - | 2016-12-14 |
| - | 6900 | - | Reserved | - | - |
// source: IANA service name and port number registry
Which program uses port 6900, and is it reachable?
Linux
sudo ss -ltnup 'sport = :6900' # process listening on 6900
sudo lsof -nP -i :6900macOS
sudo lsof -nP -i :6900
Windows (PowerShell)
Get-NetTCPConnection -LocalPort 6900 -State Listen | Select LocalAddress, OwningProcess Get-NetUDPEndpoint -LocalPort 6900 netstat -ano | findstr :6900
From another machine
nmap -p 6900 -sV <host> nc -zv <host> 6900
Block it in the firewall
sudo ufw deny 6900/tcp # Linux (ufw) New-NetFirewallRule -DisplayName "Block 6900" -Direction Inbound -LocalPort 6900 -Protocol TCP -Action Block # Windows
What is port 6900 used for?
Port 6900 is assigned by IANA to rtimeviewer (R*TIME Viewer Data Interface).
Is port 6900 TCP or UDP?
Port 6900 is registered for TCP.
Is it safe to open port 6900?
It depends on the program that listens on it. Open it only for a service you know and only to the networks that need it. Answer only the networks that need the service (no open resolvers, relays or reflectors).
How do I check if port 6900 is open?
On Linux run "ss -ltnup 'sport = :6900'", on macOS "lsof -nP -i :6900", and on Windows "netstat -ano | findstr :6900" to see the local process. From another machine, "nmap -p 6900 <host>" shows whether it is reachable.
Other network services ports
:53 DNS tcp · udp · moderate risk :135 MS RPC tcp · udp · high risk :123 NTP udp · tcp · moderate risk :67 DHCP server udp · tcp · moderate risk :111 rpcbind tcp · udp · high risk :9100 Raw printing (JetDirect) tcp · udp · high risk :631 IPP / CUPS tcp · udp · high risk :5353 mDNS udp · tcp · moderate risk