Writing an SNTP client

Unlike the previous recipe, sometimes, you don't need to get the precise time from the NTP server. You can use a simpler version of NTP called simple network time protocol.

 

How to do it...

Let us create a plain SNTP client without using any third-party library.

Let us first define two constants: NTP_SERVER and TIME1970. NTP_SERVER is the server address to which our client will connect, and TIME1970 is the reference time on January 1, 1970 (also called Epoch). You may find the value of the Epoch time or convert to the Epoch time at http://www.epochconverter.com/. The actual client creates a UDP socket (SOCK_DGRAM) to connect to the server following the UDP protocol. The client then needs to send the SNTP protocol data ('\x1b' + 47 * '\0') in a packet. Our UDP client sends and receives data using the sendto() and recvfrom() methods.

When the server returns the time information in a packed array, the client needs a specialized struct module to unpack the data. The only interesting...