Use Friendly DNS Names (Hostnames) instead of IP Addresses in TOP Server

What if your device has a host name instead of an IP address?

Sometimes the Ethernet devices you need to communicate with do not have a fixed IP address. This is a common challenge in telemetry applications for water/wastewater, oil/gas, and other industries with widely distributed control systems.

When using cellular modems to communicate to remote devices the cellular carrier often charges per-device monthly fees to obtain a fixed IP address for every device in your system. The fees associated with paying for fixed IP addresses for a large number of devices can add up quickly.

Use a DNS name instead of an IP address in TOP Server

TOP Server eliminates the cost of paying for fixed IP addresses and allows you to leverage the flexibility of dynamic IP addresses when using certain drivers that support DNS resolution.

TOP Server’s DNS Lookup functionality, also called Host Name Resolution, enables you to enter a DNS name in the format <hostname> in the Device ID field for supported drivers. TOP Server will automatically use that DNS name and your Windows computer’s configured DNS servers to convert the <hostname> to a valid IP address.

DNS resolution works with your own DNS server or a DNS service

This feature empowers you to use Dynamic DNS (i.e. and others) or DNS servers that your IT team manage to convert the defined host name to the corresponding device IP addresses.

Since TOP Server simply hands off the DNS lookup request to the DNS servers specified in your network connection settings in Windows, it will work with any DNS server, as long as your local network adapter properties are configured to use the correct DNS server.

TOP Server Ethernet drivers supporting DNS are optimized

DNS resolution for device ID is currently supported by the TOP Server Ethernet drivers shown in the diagram to the right.

DNS Host Resolution for these drivers is optimized for efficient driver reactions to changes in network address mappings for the best performance while being transparent to user applications.

This ensures that these drivers more quickly detect when a host name has been assigned a different IP address to prevent unnecessary delays in communication.

Important Notes:

  • If your DNS server/servers have delays in updating their records when your device IP address changes, those delays can affect TOP Server’s ability to reconnect quickly on a device IP address change. This can result in bad quality data and “Device Not Responding” errors while TOP Server waits for the new IP to appear in the DNS settings.
  • If you are still using TOP Server V5.7 or older, the Admin level settings Cache Lifetime and Request Pool are used to manually define how long a host name is cached before checking the DNS server and how many simultaneous requests can be made at a time to the DNS server.
    • These settings in V5.7 or older are found under the TOP Server Admin settings in the Host Resolution section.
    • Cache Lifetime - If you know your IP addresses will not change at a high frequency, set the Cache Lifetime to a higher value than the default but to a time that is shorter than the change interval of your IP address. If you are using devices with dynamic IP addresses, it is common for the provider of your dynamic IP addresses to have assigned a “Default Lease Time” for your IP addresses. Ask them what that is and set TOP Server’s Cache Lifetime setting to less than their Default Lease Time. If you do not know how often your IP addresses change, leave this setting at the default to insure maximum responsiveness. Cache lifetime can be set as high as 7200 seconds.
    • Request Pool - This setting is useful if you have a large number of channels and IP addresses that change frequently. TOP Server can perform up to 8 simultaneous DNS lookups/requests to help maintain performance. TOP Server will queue requests once the Maximum outstanding requests number is reached. Most DNS lookups are very quick, so for most users the default is sufficient. Increase the Maximum outstanding requests setting if you have a large number of devices and their IP addresses that change very frequently, or if your DNS servers are slow to respond.

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The demo is the full product once licensed. Once a client application connects to the  TOP Server, the TOP Server runtime will operate for 2 hours at a time. At the end of the 2 hour demo period, the demo timer must be reset by restarting the TOP Server runtime service.

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