Using the SNTP Client

Topic: DMD0225

Using the SNTP Client with a Time Server

What is SNTP?

The date and time for an Ethernet-equipped Do-more controller can automatically be set by retrieving the time value from a Simple Network Time Protocol (SNTP) time server. There are two levels, or tiers, of Simple Network Time Protocol (SNTP) time servers that are available on the Internet:

First-level time servers (stratum one) are primarily intended to act as source time servers for second-level time servers. The first-level time servers may also be capable of providing mission-critical time services. Some first-level time servers may have a restricted access policy.
Second-level time servers (stratum two) are intended for general SNTP time service needs. Second-level time servers usually enable public access. It is recommended that you use second-level time servers for normal SNTP time server configuration because they are usually located on a closer network that can produce faster updates.

Host Engineering does not maintain the list of time servers or recommend one time server over the other one. These links are for your reference and research to select the time server that is appropriate for your configuration. Host Engineering does recommend that you use one of the Stratum 2 Time Servers.

To find the Stratum 2 Time Servers that are available, visit the following Web site:
https://support.ntp.org/bin/view/Servers/StratumTwoTimeServers

Note: Before using the Stratum Two Time Servers, please read the "Rules Of Engagement" at the following Web site:
https://support.ntp.org/bin/view/Servers/RulesOfEngagement

How Does Do-more Provide Access to Time Servers?

Do-more controllers use the SNTP Client (NETTIME) instruction to retrieve clock and calendar information from a time server using the SNTP protocol. The time value retrieved from a time server is in UTC coordinates, so after the new time value is retrieved, the NETTIME instruction will recalculate the local time using the controller's Time Zone offset and Daylight Savings time setting, then set the controller's real-time clock to the newly calculated local time value.

The default SNTP Server IP Address of 12.69.41.165 is the SNTP server (ntp2.hosteng.com) at Host Engineering. This IP address is set in DmDesigner.Ini in the value SNTPAddress. The value stored there is not in the traditional form, it can be displayed using the 'IP Address' format in a Data View to see it in the normal format.

Note: While it is reasonable to use the default time server for testing purposes, be aware that the uptime of the default time server can not be guaranteed. It is recommended that you install your own time server or select a publicly available time server for long-term use.

The default UDP Port Number of 123 is the traditional port number used by the SNTP protocol.