DevOps & Cloud
Risk: Critical
Port 9999 — JMX Remote Monitoring / Urchin / Akka
Port 9999 is frequently designated for Java JMX remote management, Akka remoting, and local custom microservice debugging.
PORT NUMBER
9999
PROTOCOL
TCP
DEFAULT PROCESS
java
FIREWALL TARGET
9999/tcp
Instant Terminal Fixes for Port 9999
macOS & Linux Terminal
1. Check who is listening on port 9999:
sudo lsof -i :9999 || sudo ss -tulpn | grep ":9999 "2. Kill process occupying port 9999 (EADDRINUSE fix):
kill -9 $(lsof -t -i:9999)3. UFW Firewall Allow rule:
sudo ufw deny 9999/tcpWindows PowerShell (Admin)
1. Check listening port:
Get-NetTCPConnection -LocalPort 99992. Force kill process on port 9999:
Stop-Process -Id (Get-NetTCPConnection -LocalPort 9999).OwningProcess -Force3. Docker Port Forwarding Mapping:
docker run -p 9999:9999 -d my-java-appCommon Error Encountered
Failed to connect to JMX connector on port 9999: Connection refused.
Security Advisory & Hardening
Unauthenticated JMX listeners on port 9999 allow remote code execution via MBean deserialization attacks. Never expose JMX without authentication and SSL.
Frequently Asked Questions
Port 9999 Questions & Answers
Common questions regarding default services, kill commands, and firewall configurations.
Port 9999 is commonly used for JMX Remote Monitoring / Urchin / Akka. Port 9999 is frequently designated for Java JMX remote management, Akka remoting, and local custom microservice debugging.