Question: Can I make a Device Server send data to several other DS100s, all at the same time?
Answer: Yes – this is possible.
As an example you can imagine a system of several network-enabled clocks that are kept synchronized by a single timekeeping source. This source sends updating messages and it is important that those messages reach the clocks at exactly the same time (or with minimum time deviations).
First of all, you need to use DS100/EM100 firmware V3.11 or higher. This firmware supports certain new features that make multi-destination data transmissions possible.
Second, multi-destination data transmission can only be effected by using the UDP/IP transport protocol and sending UDP datagrams as broadcasts. Using TCP/IP is not possible IN PRINCIPLE because, by definition, the TCP/IP is a point-to-point protocol so “conference calls” are not possible with it. And the DS100/EM100 only allows for a SINGLE TCP/IP connection to be established at a time. Some of our Customers have suggested that, instead of using UDP broadcasts one can simply set the same IP-address in several DS100s/EM100s that must receive the data. This is a *very bad idea* and we strongly advise against using it!
To send broadcast data messages:
Set the Transport Protocol (TP) Setting of all participating DS100s/EM100s to UDP/IP
Set the Destination IP-address (DI) Setting of the sending DS100/EM100 to 255.255.255.255
Set the Broadcast UDP (BU) Setting of all receiving DS100s/EM100s to 1 (enabled). If this is not done the DS100/EM100 will ignore the UDP/IP packets sent in the broadcast mode (and this is a way to prevent certain DS100s/EM100s from receiving the data).
Such a system is not without its weak points:
Delivery of messages is not reliable. There is no 100% guarantee that all UDP datagrams will be able to reach all destination DS100s/EM100s each time. In our example (the clock synchronization) this is not so important because it is OK to lose a certain percentage of the synchronizing messages.
Broadcasts, by their nature, cannot pass through the routers (bridges, firewall, etc.) and hence can only reach the DS100s/EM100s located on the same network segment with the sender.
