Existe sempre o Protocolo do dia
Na 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).