Solution:
Root Cause: Dynamic Host IP Drift or Unbound Socket Interface
Inbound packets forwarded by the router are dropped because the destination device's internal IP address changed via DHCP lease expiration, or the application is listening exclusively on the
127.0.0.1 (localhost) loopback interface instead of
0.0.0.0 (all interfaces).
Step-by-Step Fix:
1.Assign a Static IP or DHCP Reservation:
Log into your router's admin panel and navigate to DHCP Server > Address Reservation.Map the target machine's MAC address to a fixed local IP address (e.g., 192.168.1.150).2.Verify Target Application Listening Socket:
Confirm your target service is actively listening on all local network interfaces (0.0.0.0 or ::), not restricted to 127.0.0.1.On Windows (CMD Admin): cmd
netstat -ano | findstr :<your_port_number>
On Linux: bash
sudo ss -tulpn | grep :<your_port_number>
3.Update Router Port Forwarding Table:
Re-verify that External Port, Internal Port, Protocol (TCP/UDP), and Target Host IP strictly match your application's requirements.