EPMD (Erlang Port Mapper)
What is Port 4369?
Port 4369 is used by EPMD (Erlang Port Mapper Daemon), a name server used by Erlang and Elixir distributed systems to discover nodes and their ports. EPMD runs on each host where Erlang nodes are present and maintains a mapping of node names to the TCP ports they listen on. When one Erlang node wants to communicate with another, it first contacts EPMD to discover the target node's port. EPMD is essential for RabbitMQ clusters, CouchDB, Riak, and any system built on the Erlang/OTP platform. Since Erlang's distributed computing capabilities are a core feature of the BEAM virtual machine, EPMD is fundamental to Erlang-based distributed systems.
Common Uses
- RabbitMQ cluster node discovery
- Erlang/Elixir distributed node communication
- CouchDB cluster coordination
- Distributed Erlang application deployment
Technical Details
Copy-paste commands to check port 4369 (EPMD (Erlang Port Mapper)) from your terminal
Test connectivity
nc -zv example.com 4369
curl -v --max-time 5 http://example.com:4369/
telnet example.com 4369
nmap -p 4369 -sV example.com
(echo > /dev/tcp/example.com/4369) 2>/dev/null && echo "open" || echo "closed"
Open port in firewall
sudo ufw allow 4369/tcp
sudo iptables -A INPUT -p tcp --dport 4369 -j ACCEPT
sudo firewall-cmd --permanent --add-port=4369/tcp && sudo firewall-cmd --reload
Security Considerations
EPMD provides information about running Erlang nodes and their ports. Restrict access to EPMD using firewall rules. In production, use the Erlang distribution's built-in cookie authentication. Consider using alternative discovery mechanisms that don't require exposing EPMD. Monitor for unauthorized node connection attempts.
Popular Ports Reference
The most commonly used and referenced network ports