Ububut 18.0.4 LTS：无法在端口 9 上启动 TCP/UDP 丢弃服务和在端口 37 上启动时间服务

Question

我有 ubuntu 客户端 18.0.4，无法在端口 9 和端口 37 上 telnet 本地主机。

root@ubuntu:~# telnet 127.0.0.1 37
telnet: Unable to connect to remote host: Connection refused
root@ubuntu:~# telnet 127.0.0.1 9
telnet: Unable to connect to remote host: Connection refused
root@ubuntu:~# cat /etc/xinetd.d/time
i# default: off
# description: An RFC 868 time server. This protocol provides a
# site-independent, machine readable date and time. The Time service sends back
# to the originating source the time in seconds since midnight on January first
# 1900.
# This is the tcp version.
service time
{
    disable     = no <<<<<<<<<<<<<<<<<<<<<<<<<<<<,I have changed to no
    type        = INTERNAL
    id      = time-stream
    socket_type = stream
    protocol    = tcp
    user        = root
    wait        = no
}

# This is the udp version.
service time
{
    disable     = no
    type        = INTERNAL
    id      = time-dgram
    socket_type = dgram
    protocol    = udp
    user        = root
    wait        = yes
}
root@ubuntu:~#
root@ubuntu:~# cat /etc/xinetd.d/discard
i# default: off
# description: An RFC 863 discard server.
# This is the tcp version.
service discard
{
    disable     = no
    type        = INTERNAL
    id      = discard-stream
    socket_type = stream
    protocol    = tcp
    user        = root
    wait        = no
}

# This is the udp version.
service discard
{
    disable     = no
    type        = INTERNAL
    id      = discard-dgram
    socket_type = dgram
    protocol    = udp
    user        = root
    wait        = yes
}
root@ubuntu:~#

我重启过 xinetd 几次，但都没有成功。此外，我还在 /etc/services 上配置了服务。

root@ubuntu:~# cat /etc/services | grep 37
time        37/tcp      timserver
time        37/udp      timserver

root@ubuntu:~# cat /etc/services | grep 9
discard     9/tcp       sink null
discard     9/udp       sink null

请问有什么建议吗？