Add GATEWAY_UDP_PORT environment variable with default value 51900 to replace hardcoded port 51820. Update DEFAULT_GATEWAY_ENDPOINT in .env.example to use new port. Add UDP port mapping to gateway service in docker-compose using GATEWAY_UDP_PORT. Add NEXAVPN_GATEWAY_LISTEN_PORT environment variable to gateway container. Update gateway-entrypoint.sh to use GATEWAY_LISTEN_PORT variable in bootstrap payload and WireGuard interface configuration.