All ports
Port3900/UDP
udt_osPort
3900
Protocol
UDP
Category
Registered
Service
udt_os
What is port 3900?
Port 3900/UDP is a Registered port, registered with IANA for specific applications. It is associated with the udt_os service.
Unidata UDT OS
Useful commands
nmapnmap -p 3900 -sV example.comnetcatnc -zv example.com 3900curlcurl -v http://example.com:3900/telnettelnet example.com 3900bash(echo > /dev/udp/example.com/3900) 2>/dev/nullFirewall commands
UFWAllow
sudo ufw allow 3900/udpDeny
sudo ufw deny 3900/udpiptablesAllow
sudo iptables -A INPUT -p udp --dport 3900 -j ACCEPTDeny
sudo iptables -D INPUT -p udp --dport 3900 -j ACCEPTfirewalldAllow
sudo firewall-cmd --permanent --add-port=3900/udpWindowsAllow
netsh advfirewall firewall add rule name="Open Port 3900" dir=in action=allow protocol=UDP localport=3900Security Risks
- Unauthorized access to the service
- Data exposure if the service is unauthenticated
- Outdated versions with vulnerabilities
- Incorrect service configuration
Frequently Asked Questions
What service runs on port 3900/UDP?
Port 3900/UDP is associated with the udt_os service. Unidata UDT OS
Is it safe to expose port 3900 to the Internet?
It depends on the service and configuration. Port 3900 (udt_os) is a Registered port. If you need to expose it, keep the service updated, use strong authentication, and configure a firewall. It's always recommended to restrict access by IP when possible.
How do I check if port 3900 is open?
You can use nmap: `nmap -p 3900 -sV example.com`, netcat: `nc -zv example.com 3900`, or the bash command: `(echo > /dev/udp/example.com/3900) 2>/dev/null && echo "Open" || echo "Closed"`.
How do I open or close port 3900 on my firewall?
On Linux with UFW: `sudo ufw allow 3900/udp` (open) or `sudo ufw deny 3900/udp` (close). With iptables: `sudo iptables -A INPUT -p udp --dport 3900 -j ACCEPT`. On Windows: `netsh advfirewall firewall add rule name="Open Port 3900" dir=in action=allow protocol=UDP localport=3900`.
What applications and services use port 3900?
Port 3900/UDP is used by the udt_os service. Specific uses depend on the software and configuration. Check our related tools section for more information.