What is the expected response time for Spacebridge? It seems to be about a 45 second round trip from when I send data to my device and I get a response back. It usually takes about 20 seconds or so for my device to receive the data, it responds in less than a second.
Using a 4G Cat1 modem from Nimbelink.
My MQTT connection does not seem to suffer from the same delays.
Hey are you using our API to send individual messages down to the device, or using the Spacebridge client to forward a port?
Some high latency is expected for inbound connections like that with some modems as the modem can sometimes go into a low power state for a bit if the connection is idle and we may not be able to route traffic to it until it jumps back on the tower again. You can look to see if the modem has eDRX or PSM and turn those features off. Sometimes that helps.
There is also some latency just for the network to find the correct inbound route to the modem if it hasn’t talked to it for a while.
MQTT tends to be faster since it is always holding the TCP connection open and sending keep alives so the connection never goes idle.
I have seen the same issue with my devices connecting with 3G, LTE Cat3, Cat1 and CatM1. The devices maintain a persistent TCP connection and messages from the device instantaneously arrive at our server, and messages sent using the Hologram API also quickly arrive at the device.
After a SpaceBridge tunnel connection is established to the device (a terminal SSH or Telnet connection), if I’m interacting with the device I get a reasonable response, but if I let the session idle for 30 seconds or so, then it takes 5 to 10 seconds before I get a response from the device, and then it’s quick until I pause again. I have seen this with both AT&T and T-Mobile.
If I use these devices on MVNOs that provide a VPN to a static IP, I don’t see this issue, so I think it’s something unique to the Hologram Spacebridge implementation.
I was running MQTT at the same time as I was using the Spacebridge client. I would assume that MQTT running would have kept the modem from going to sleep and the connection to the tower active. I will do some more testing and see if I can get a time estimate on the latency.
I do know when my modem sends data to Hologram it can take a full 10 seconds for hologram to reply with the [0,0] indicating that the message was received.
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