Channels and Group Chat

How MeshCore channels work, the public channel key, and creating your own private group

Direct messages are one to one. Channels are how a group talks - a family, a hiking club, a village, or the whole regional network.

What a channel actually is

A channel in MeshCore is nothing more than a name and a shared secret key. Anyone holding the same key can read and post to the channel. There is no server, no membership list, no admin.

Why this matters: Adding someone to a channel means giving them the key. Removing someone means creating a new channel with a new key and giving that to everyone else. It is simple, robust, and entirely in your hands.

The public channel

MeshCore ships with a well-known public channel that every node can use out of the box. Its key is not a secret - it is published so that strangers can find each other:

Hex:    8b3387e9c5cdea6ac9e5edbaa115cd72
Base64: izOH6cXN6mrJ5e26oRXNcg==

Note the third character of the Base64 string is a capital letter O, not a zero. That catches people out.

Use it for: saying hello to the local mesh, testing, emergencies, coordinating with strangers.

Do not use it for: anything private. Assume everyone within radio range can read it, because they can.

Creating your own channel

In the MeshCore app, add a channel and either generate a new random key or type in a shared one.

To share it with your group, the easiest route is a QR code - the app will generate one for you, and the other person scans it. No typing, no transcription errors.

A worked example - a family channel:

1. On your phone, create a channel called Family
2. Let the app generate a random key
3. Show the QR code to each family member and have them scan it
4. Everyone with the key now sees every message posted to that channel

Channels always flood

This is the important technical detail.

Direct messages learn a path and then follow it, which is efficient. Channel messages cannot do that - a channel has no single destination, so every channel message floods across the mesh.

Why this matters:

• Channel traffic is expensive. Ten people chatting on a channel across a regional mesh is a lot of airtime
• Repeater operators can and do limit how far floods travel, with set flood.max <hops>
• On a busy network, prefer direct messages for one to one conversation and keep channels for things the group genuinely needs to see

Sensible channel etiquette

• Keep messages short. Every character costs airtime for everyone
• Do not use channels for testing. Test with direct messages to your own second node
• Respect the local public channel. It is often used for coordination and emergencies
• Do not bridge a channel to the internet without telling the people on it

Limiting flood range on your repeater

From the repeater console:

set flood.max 3

This caps how many hops a flooded packet will travel through your repeater. On a small local mesh, 3 is generous. On a dense regional network, operators sometimes go lower.

Try it Yourself

1. Add the public channel to your client and post a short hello. Does anyone answer?
2. Create a private channel, generate a key, and export the QR code. Save it somewhere safe.
3. Challenge: with log start running on your repeater, post a channel message and then read the log. Can you see the flood?

Common Issues

Problem: I typed the public channel key in and it does not work.

Solution: Check the third character of the Base64 key - it is a capital O, not a zero. Or use the hex version instead.

Why: The two characters are nearly identical in most fonts and it is the single most common transcription error.

Problem: My friend cannot see my channel messages.

Solution: Confirm you both have the exact same key, and that your radio settings match.

Why: A channel with a different key is a different channel, even if the name is identical. The name is only a label.

Problem: My channel messages take ages to arrive.

Solution: Nothing is wrong. Consider using a direct message instead.

Why: Channel messages flood, which means every repeater in range queues and retransmits them. On a busy mesh that queue can be long.

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