测量远程服务器的系统时钟(时间)

Question

哪些网络协议可以用来测量远程服务器的系统时钟(时间)？到目前为止，我已经：

• NTP查询
• TCP时间戳
• HTTP标头

还有其他的吗？

Answer 1

总有一个日间议定书

来自RFC：

A useful debugging and measurement tool is a daytime service.  A daytime
service simply sends a the current date and time as a character string
without regard to the input.

TCP Based Daytime Service

One daytime service is defined as a connection based application on
TCP.  A server listens for TCP connections on TCP port 13.  Once a
connection is established the current date and time is sent out the
connection as a ascii character string (and any data received is
thrown away).  The service closes the connection after sending the
quote.

UDP Based Daytime Service

Another daytime service service is defined as a datagram based
application on UDP.  A server listens for UDP datagrams on UDP port
13.  When a datagram is received, an answering datagram is sent
containing the current date and time as a ASCII character string (the
data in the received datagram is ignored).