好像9091被端口占用了，内网ip访问不了，外网域名也访问不了，请问有什么方法可以改默认端口或者查看什么程序占用了端口吗

Fri Sep 20 00:15:17 CST 2019
Starting transmission command /volume1/@appstore/transmission/bin/transmission-daemon -g /volume1/@appstore/transmission/var/ -x /volume1/@appstore/transmission/var/transmission.pid -e /volume1/@appstore/transmission/var/transmission.log
[2019-09-20 00:15:18.333] Transmission 2.94 (d8e60ee44f) started (session.c:740)
[2019-09-20 00:15:18.333] RPC Server Adding address to whitelist: 127.0.0.1 (rpc-server.c:971)
[2019-09-20 00:15:18.333] RPC Server Serving RPC and Web requests on port 127.0.0.1:9091/transmission/ (rpc-server.c:1213)
[2019-09-20 00:15:18.333] RPC Server Password required (rpc-server.c:1220)
[2019-09-20 00:15:18.333] UDP Failed to set receive buffer: requested 4194304, got 425984 (tr-udp.c:84)
[2019-09-20 00:15:18.334] UDP Please add the line "net.core.rmem_max = 4194304" to /etc/sysctl.conf (tr-udp.c:89)
[2019-09-20 00:15:18.334] UDP Failed to set send buffer: requested 1048576, got 425984 (tr-udp.c:95)
[2019-09-20 00:15:18.334] UDP Please add the line "net.core.wmem_max = 1048576" to /etc/sysctl.conf (tr-udp.c:100)
[2019-09-20 00:15:18.334] DHT Generating new id (tr-dht.c:311)
[2019-09-20 00:15:18.334] Using settings from "/volume1/@appstore/transmission/var/" (daemon.c:528)
[2019-09-20 00:15:18.334] Saved "/volume1/@appstore/transmission/var/settings.json" (variant.c:1266)
[2019-09-20 00:15:18.334] Saved pidfile "/volume1/@appstore/transmission/var/transmission.pid" (daemon.c:543)
[2019-09-20 00:15:18.334] transmission-daemon requiring authentication (daemon.c:554)
[2019-09-20 00:15:18.334] Port Forwarding (NAT-PMP) initnatpmp succeeded (0) (natpmp.c:70)
[2019-09-20 00:15:18.334] Port Forwarding (NAT-PMP) sendpublicaddressrequest succeeded (2) (natpmp.c:70)
[2019-09-20 00:15:18.334] Port Forwarding State changed from "Not forwarded" to "Starting" (port-forwarding.c:92)
[2019-09-20 00:15:25.334] Port Forwarding State changed from "Starting" to "???" (port-forwarding.c:92)
[2019-09-20 00:15:43.334] DHT Attempting bootstrap from dht.transmissionbt.com (tr-dht.c:249)
这个是启动tr时候的日志