Is it safe to open
Never leave remote access open to the whole internet: bots try passwords around the clock. Put it behind a VPN (WireGuard, IPsec), or allow only your own addresses, use keys or long passwords, and enable brute-force protection (fail2ban, account lockout).
How to open port 3389
Open to everyone
# Linux iptables iptables -A INPUT -p tcp --dport 3389 -j ACCEPT iptables -A INPUT -p udp --dport 3389 -j ACCEPT # Ubuntu ufw ufw allow 3389/tcp ufw allow 3389/udp # firewalld firewall-cmd --permanent --add-port=3389/tcp && firewall-cmd --reload firewall-cmd --permanent --add-port=3389/udp && firewall-cmd --reload # MikroTik /ip firewall filter add chain=input protocol=tcp dst-port=3389 action=accept place-before=0 comment="port 3389" /ip firewall filter add chain=input protocol=udp dst-port=3389 action=accept place-before=0 comment="port 3389" # Windows (PowerShell) New-NetFirewallRule -DisplayName "Port 3389 TCP" -Direction Inbound -Protocol TCP -LocalPort 3389 -Action Allow New-NetFirewallRule -DisplayName "Port 3389 UDP" -Direction Inbound -Protocol UDP -LocalPort 3389 -Action Allow
Only for your addresses
# allow only one address or network (replace 203.0.113.0/24) iptables -A INPUT -p tcp --dport 3389 -s 203.0.113.0/24 -j ACCEPT iptables -A INPUT -p udp --dport 3389 -s 203.0.113.0/24 -j ACCEPT iptables -A INPUT -p tcp --dport 3389 -j DROP iptables -A INPUT -p udp --dport 3389 -j DROP ufw allow from 203.0.113.0/24 to any port 3389 proto tcp ufw allow from 203.0.113.0/24 to any port 3389 proto udp /ip firewall filter add chain=input protocol=tcp dst-port=3389 src-address=203.0.113.0/24 action=accept /ip firewall filter add chain=input protocol=udp dst-port=3389 src-address=203.0.113.0/24 action=accept /ip firewall filter add chain=input protocol=tcp dst-port=3389 action=drop /ip firewall filter add chain=input protocol=udp dst-port=3389 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 ':3389 ' netstat -ano | findstr :3389 # Windows lsof -i :3389 # macOS # test from another machine nc -vz example.com 3389