We tested a messaging app used by Hong Kong protesters that works without an internet connection
Bridgefy is a Bluetooth mesh network app trending in Hong Kong
The Hong Kong protests have been as much about battles on the internet as on the streets.
We decided to test it on the streets of Hong Kong.
That’s when I launched the Bridgefy app and turned on the Broadcast feature, which puts all the people within range of each other into one group. This could allow a group to spread out across a wide area while still being able to exchange messages.
I sent the first message and waited. After 30 minutes, I received a reply: “Fight for freedom! Stand with Hong Kong!”
The good news is it worked! I could now send and receive messages without having an internet connection.
And then I discovered a completely different problem: A chat app isn’t much use if nobody’s actually chatting. I ended up only getting five replies to my queries.
Meanwhile, Telegram groups were buzzing with activity, including updates on the vandalism committed by some protesters on the subway and their next moves.
Even when I did get messages on Bridgefy, I encountered issues. The arrival times of messages would easily get mixed up, putting the conversation out of order (something I saw when I tested the app in the office, too). And the Broadcast function stops working as soon as you exit the app, so don’t expect background notifications with important updates.
Bridgefy uses Bluetooth to communicate, creating a mesh network of devices to pass on messages.
If that was a bit of meaningless word salad to you, think about it this way: Imagine that you’re at one end of a human chain that stretches over a mile long. You can’t shout loud enough to be heard by the person at the far end of the chain. But you can get your message to the person standing right next to you -- who can tell the person next to them, and so on, until it reaches the other end.
That’s effectively how a mesh network works: Each device passes information on to the next device, and the next, and the next. In theory, as long as you have enough devices in range, you can bridge huge gaps with lots of tiny hops between phones… assuming those phones are using Bridgefy, of course.
But that’s also the big disadvantage of a mesh network, which is that you’re reliant on an ad-hoc network where a gap in coverage can cause huge issues. To use the human chain analogy again: It doesn’t matter if people on your end are standing arm-in-arm if there’s a huge gap in the middle. If the message can’t bridge that gap -- or does so very slowly -- the system won’t work.
We saw this in action when we conducted a quick test in the office among the Abacus team. I stood at one end, Xinmei stood at the other, and Thomas was in the middle -- bridging the gap between us. In theory, any message I send to Xinmei would be relayed by Thomas’s phone, as would any message from Xinmei to me.
Perhaps the distances were too great, or there was too much interference from other devices. But in both direct messaging and Broadcast mode (with Airplane Mode switched on), the messages traveled slowly at best -- and at worst, sometimes out of order entirely, resulting in an utterly confusing conversation.
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