Command polling

When I read about the command polling feature of clients, it seems to say that enabling command polling will allow for quicker response times for clients that cannot receive the UDP ping. Well “quicker” to me means that clients will eventually receive policy from relays even without being able to receive UDP pings and with no command polling enabled. Is this correct? and if so, what is the mechanism/timing of this? Does the client attempt contact every 12 hours with its relay if it hears nothing, for example? I’m asking this specifically for laptops that will potentially be on the internet connecting to a relay in a DMZ. I would imagine that even if the outer firewall is configured to allow UDP traffic on port 52311 out to the internet that it is probably a good idea to use command polling on those devices because of other routers outside their control that might block UDP? Also I was wondering if the BES Server to relay, and relay to relay communication also requires the UDP pings on 52311?

Command polling definitely can speed things up if UDP messages can’t get through.

The client does do a command poll every time it re-registers but that by default is a 6 hour window.

Relays and Server use TCP to communicate but if a relay is blocked from being able to connect (say it is behind a NAT) there is also a form of command polling available for the Relay.

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When you enable CommandPolling, you also need to specify how frequently the client will poll.

To enable CommandPolling every 6 hours(default), you would set the following settings…
_BESClient_Comm_CommandPollEnable="True"
_BESClient_Comm_CommandPollIntervalSeconds=21600

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There’s a task to enable it in the BES Support site, this will allow you specify the polling interval as a parameter.

Only the ‘last leg’ from the relay to client uses the UDP ping - the other legs … server to relay, relay to relay, use TCP (http). As @AlanM says if you can’t ip address properly on these other legs then command polling will fix that.

A qualified ‘yes’, without command polling enabled the re-registration event (every 6 hours) will establish a communication from the client to its relay. This is TCP.

And everything is on 52311 by default.

This fixlet will set command polling to once an hour only for clients that do not get UDP notifications:


Even with clients effectively doing a poll for commands every 6 hours during re-registration, it isn’t a bad idea to set all clients to use command polling for every 6 hours. It won’t cause them to do it more often, but it will set a ceiling. The primary impact of command polling is on the relays and not the root server, so it might be reasonable to set it to something like 3 hours on all clients, but I would start out conservatively and go from there.

Even computers that do receive UDP notifications normally will miss them when they are asleep or powered down.