Is it safe to open
SIP and VoIP ports are scanned constantly by toll-fraud bots looking for weak extensions. Allow only your provider's IP addresses on the firewall where possible, use long SIP passwords, fail2ban, and disable SIP ALG on the router.
How to open port 5004
Open to everyone
# Linux iptables iptables -A INPUT -p udp --dport 5004 -j ACCEPT # Ubuntu ufw ufw allow 5004/udp # firewalld firewall-cmd --permanent --add-port=5004/udp && firewall-cmd --reload # MikroTik /ip firewall filter add chain=input protocol=udp dst-port=5004 action=accept place-before=0 comment="port 5004" # Windows (PowerShell) New-NetFirewallRule -DisplayName "Port 5004 UDP" -Direction Inbound -Protocol UDP -LocalPort 5004 -Action Allow
Only for your addresses
# allow only one address or network (replace 203.0.113.0/24) iptables -A INPUT -p udp --dport 5004 -s 203.0.113.0/24 -j ACCEPT iptables -A INPUT -p udp --dport 5004 -j DROP ufw allow from 203.0.113.0/24 to any port 5004 proto udp /ip firewall filter add chain=input protocol=udp dst-port=5004 src-address=203.0.113.0/24 action=accept /ip firewall filter add chain=input protocol=udp dst-port=5004 action=drop
If the server is behind a router, you also need a port forward (dst-nat). Behind ISP CGNAT (100.64.0.0/10 on the WAN) forwarding will not help: you need a public IP or a VPN.
What is listening
Check on the server
# what listens on the port ss -lntup | grep ':5004 ' netstat -ano | findstr :5004 # Windows lsof -i :5004 # macOS