Time Server rfc868

Rfc868

Network Working Group                                    J. Postel - ISIRequest for Comments: 868                           K. Harrenstien - SRI                                                                May 1983                             Time ProtocolThis RFC specifies a standard for the ARPA Internet community.  Hosts onthe ARPA Internet that choose to implement a Time Protocol are expectedto adopt and implement this standard.This protocol provides a site-independent, machine readable date andtime.  The Time service sends back to the originating source the time inseconds since midnight on January first 1900.One motivation arises from the fact that not all systems have adate/time clock, and all are subject to occasional human or machineerror.  The use of time-servers makes it possible to quickly confirm orcorrect a system's idea of the time, by making a brief poll of severalindependent sites on the network.This protocol may be used either above the Transmission Control Protocol(TCP) or above the User Datagram Protocol (UDP).When used via TCP the time service works as follows:   S: Listen on port 37 (45 octal).   U: Connect to port 37.   S: Send the time as a 32 bit binary number.   U: Receive the time.   U: Close the connection.   S: Close the connection.   The server listens for a connection on port 37.  When the connection   is established, the server returns a 32-bit time value and closes the   connection.  If the server is unable to determine the time at its   site, it should either refuse the connection or close it without   sending anything.Postel                                                          [Page 1]RFC 868                                                         May 1983Time Protocol                                                           When used via UDP the time service works as follows:   S: Listen on port 37 (45 octal).   U: Send an empty datagram to port 37.   S: Receive the empty datagram.   S: Send a datagram containing the time as a 32 bit binary number.   U: Receive the time datagram.   The server listens for a datagram on port 37.  When a datagram   arrives, the server returns a datagram containing the 32-bit time   value.  If the server is unable to determine the time at its site, it   should discard the arriving datagram and make no reply.The TimeThe time is the number of seconds since 00:00 (midnight) 1 January 1900GMT, such that the time 1 is 12:00:01 am on 1 January 1900 GMT; thisbase will serve until the year 2036.For example:   the time  2,208,988,800 corresponds to 00:00  1 Jan 1970 GMT,             2,398,291,200 corresponds to 00:00  1 Jan 1976 GMT,             2,524,521,600 corresponds to 00:00  1 Jan 1980 GMT,             2,629,584,000 corresponds to 00:00  1 May 1983 GMT,        and -1,297,728,000 corresponds to 00:00 17 Nov 1858 GMTPostel                                                          [Page 2]