添加白名单,要不然就会提示403，被拒绝
打开配置文件：sudo vim /etc/transmission-daemon/settings.json

"rpc-whitelist": "127.0.0.1,192.168.2.103"

192.168.2.103就是我的在web登录机器的ip,然后重启服务就可以了

udp 缓冲区的问题
错误提示(日志在：/var/log/daemon.log 中)：

UDP Failed to set receive buffer: requested 4194304, got 327680 (tr-udp.c:78)
UDP Failed to set send buffer: requested 1048576, got 327680 (tr-udp.c:89)

是UDP接收和发送的缓冲区太小的问题；
解决方法如下：

sudo sysctl -w net.core.rmem_max=4195328
sudo sysctl -w net.core.wmem_max=4195328
sudo sysctl -w net.core.wmem_default=4195328
sudo sysctl -w net.core.rmem_default=4195328
sudo sysctl -w net.ipv4.udp_mem="4195328 4195328 4195328"
sudo sysctl -w net.ipv4.udp_rmem_min=4195328
sudo sysctl -w net.ipv4.udp_wmem_min=4195328