All ports
Port513/UDP
whoPort
513
Protocol
UDP
Category
Well-Known
Service
who
What is port 513?
Port 513/UDP is a Well-Known port, assigned by IANA for widely recognized services. It is associated with the who service.
maintains data bases showing who's logged in to machines on a local net and the load average of the machine
Useful commands
nmapnmap -p 513 -sV example.comnetcatnc -zv example.com 513curlcurl -v http://example.com:513/telnettelnet example.com 513bash(echo > /dev/udp/example.com/513) 2>/dev/nullFirewall commands
UFWAllow
sudo ufw allow 513/udpDeny
sudo ufw deny 513/udpiptablesAllow
sudo iptables -A INPUT -p udp --dport 513 -j ACCEPTDeny
sudo iptables -D INPUT -p udp --dport 513 -j ACCEPTfirewalldAllow
sudo firewall-cmd --permanent --add-port=513/udpWindowsAllow
netsh advfirewall firewall add rule name="Open Port 513" dir=in action=allow protocol=UDP localport=513Security 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- Outdated versions with vulnerabilities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 513/UDP?
Port 513/UDP is associated with the who service. maintains data bases showing who's logged in to machines on a local net and the load average of the machine
Is it safe to expose port 513 to the Internet?
It depends on the service and configuration. Port 513 (who) is a Well-Known 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 513 is open?
You can use nmap: `nmap -p 513 -sV example.com`, netcat: `nc -zv example.com 513`, or the bash command: `(echo > /dev/udp/example.com/513) 2>/dev/null && echo "Open" || echo "Closed"`.
How do I open or close port 513 on my firewall?
On Linux with UFW: `sudo ufw allow 513/udp` (open) or `sudo ufw deny 513/udp` (close). With iptables: `sudo iptables -A INPUT -p udp --dport 513 -j ACCEPT`. On Windows: `netsh advfirewall firewall add rule name="Open Port 513" dir=in action=allow protocol=UDP localport=513`.
What applications and services use port 513?
Port 513/UDP is used by the who service. Specific uses depend on the software and configuration. Check our related tools section for more information.