[D66] GeoTalk 📡 : Pseudo-HAM Radio & Text Messaging — Geo-grouped by Postal Code

[René Oudeweg]

reinold at NUC1:~/Projects/geotalk$ ./charlie.sh

    ██████╗  ███████╗  ██████╗  ████████╗  █████╗  ██╗      ██╗  ██╗
   ██╔════╝  ██╔════╝ ██╔═══██╗ ╚══██╔══╝ ██╔══██╗ ██║      ██║ ██╔╝
   ██║  ███╗ █████╗   ██║   ██║    ██║    ███████║ ██║      █████╔╝
   ██║   ██║ ██╔══╝   ██║   ██║    ██║    ██╔══██║ ██║      ██╔═██╗
   ╚██████╔╝ ███████╗ ╚██████╔╝    ██║    ██║  ██║ ███████╗ ██║  ██╗
    ╚═════╝  ╚══════╝  ╚═════╝     ╚═╝    ╚═╝  ╚═╝ ╚══════╝ ╚═╝  ╚═╝
   📡  Geo-grouped pseudo-HAM radio & text  •  v1.3.1
   Type /help for commands  •  #59** Venlo  •  #1***?? Amsterdam

Relay connected → 127.0.0.1:5073
   Mode: relay unicast UDP  (multicast disabled)

Joined #5944  → relay=127.0.0.1:5073
   Region: NL · Venlo regio
22:41 → BOB online (NL · Venlo regio) #5944
22:41 → ALICE online (NL · Venlo regio) #5944
22:42 → BOB online (NL · Venlo regio) #5944
22:42 → ALICE online (NL · Venlo regio) #5944
CHARLIE@#5944>


On 3/7/26 20:54, René Oudeweg wrote:
> [Voila: een kersverse pseudo-HAM CLI tool dat elke postcode of postcode 
> regio in een tekst- en audiokanaal tovert. Heeft Henk van Lingen 
> interesse om een de relay server op tuxtown.net te installeren? Dan 
> kunnen we texten en broadcasten over het internet zonder dure HAM 
> radio's en de nodige licenties voor zendamateurs. :-) Dat is weer eens 
> wat anders dan knipselkrantjes maken...
> 
> PS: Enige Linux hack ervaring is een must.
> 
> Nog geen GUI. Niet getest met Windows of MacOS. Dus ik neem aan dat 
> weinigen op deze lijst hiermee overweg kunnen. Maar goed, probeer het 
> eens zou ik zeggen.
> 
> retour,
> 
> René Oudeweg
> 
> ]
> 
> 
> -- 
> 
> https://github.com/juggao/geotalk
> 
> GeoTalk 📡
> 
> Pseudo-HAM Radio & Text Messaging — Geo-grouped by Postal Code
> 
> GeoTalk is a Linux CLI tool that turns any postal code into a radio 
> channel. Users in the same postal zone share a UDP group; voice (PTT) 
> and text messages are broadcast to everyone on that channel — like a 
> local walkie-talkie net. Works on a LAN via IP multicast, or across the 
> internet via a relay server.
> 
> Version 1.3.1
> 
> ## Features
> 
> | | Feature | Details |
> |---|---|---|
> | 📮 | Exact postal channels | Any EU/UK postal code is a channel — 
> `#59601`, `#
> 1234AB`, `#SW1A` |
> | 🔍 | Wildcard channels | `#59**` = Venlo region · `#750**` = Paris · 
> `#1***??`
>   = Amsterdam |
> | 🧩 | Regex channels | `/^[0-9]{4}[A-Z]{2}$/` — full Python regex 
> between `//`
> |
> | 🗺️ | Region database | 120+ EU postal prefixes resolved to human- 
> readable regio
> n names |
> | 💬 | Text messaging | Instant broadcast to all channel members |
> | 🎙️ | Push-to-Talk (PTT) | Real mic audio over UDP (16 kHz PCM) |
> | 📻 | Multi-channel RX | Subscribe to many channels at once; all arrive 
> in one
> terminal |
> | 🔎 | Channel scan | `/scan 59**` — probe a region for live users, 
> results stre
> am in real time |
> | 🌐 | Relay mode | `--relay HOST` for internet use — no multicast 
> routing neede
> d |
> | 🔄 | Auto-reconnect | Client reconnects to relay with exponential 
> back-off |
> | 🔒 | LAN mode | Pure peer-to-peer UDP multicast, zero infrastructure 
> required
> |
> 
> 
> -- 
> 
> 
> JOINING A CHANNEL
> 
> You join a channel by typing its postal code prefixed with #:
> 
>      #5912       join the exact channel for postcode 5912
>      #5944AV     join the exact channel for postcode 5944AV
> 
> Anyone else on the same LAN (or connected to the same relay) who has 
> joined #5912 will see your messages and hear your voice.
> 
> 
> WILDCARD CHANNELS
> 
> You can also join a region rather than a single postcode:
> 
>      #591*       joins the Venlo Centrum region (5910–5919, 591A–591Z)
>      #59**       joins the entire Venlo regio (5900–5999 and more)
>      #750**      joins all Paris postcodes
> 
> The * matches exactly one character. The ** matches one or more. So 
> #591* covers 5910, 5911, 5912 ... 591Z as a single subscription.
> 
> 
> A CONCRETE EXAMPLE
> 
> Suppose three people are running GeoTalk:
> 
>      BOB    joined #5912
>      ALICE  joined #5913
>      CHARLIE joined #591*
> 
> BOB and ALICE are on different exact channels — they cannot hear each 
> other directly. But CHARLIE, on the wildcard #591*, is subscribed to a 
> channel whose pattern covers both 5912 and 5913. BOB sends a message on 
> #5912 → CHARLIE receives it. ALICE sends a message on #5913 → CHARLIE 
> receives it too.
> 
> 
> SCANNING FOR ACTIVE USERS
> 
> If CHARLIE wants to discover who is active in the Venlo area before 
> joining, he can run a scan:
> 
>      /scan 591*
> 
> GeoTalk expands 591* into all 36 concrete codes (5910–5919, 591A–591Z) 
> and sends a probe to each multicast group. BOB's client receives the 
> probe on #5912 and replies automatically. ALICE's client receives it on 
> #5913 and replies. Within a few seconds CHARLIE sees:
> 
>      ► #5912    BOB     NL · Venlo Centrum
>      ► #5913    ALICE   NL · Venlo Centrum
> 
> He can then join either channel directly, or join #591* to receive from 
> both simultaneously.
> 
> A broader scan works the same way:
> 
>      /scan 59**    → probes all 5900–5999 (100 channels) plus 
> alphanumeric variants
>      /scan 750**   → probes all Paris postal codes
> 
> 
> PUSH-TO-TALK
> 
> Voice works like a walkie-talkie. Press Ctrl+T to toggle the mic on, 
> speak, press Ctrl+T again to release. Everyone on the channel hears you 
> in real time. Press Ctrl+Y to mute incoming audio if you only want to type.
> 
> 
> RELAY MODE (internet use)
> 
> For use across the internet, one person runs the relay server:
> 
>      python3 geotalk-relay.py --port 5073
> 
> Everyone else connects to it:
> 
>      python3 geotalk.py --nick PA3XYZ --relay relay.example.com
> 
> The relay routes all traffic — text, voice, and scans — between 
> connected clients. It requires only a single UDP port (5073) open on the 
> server.
> 
> 
> Let me know if you have any questions.
> 
> Best regards,
> 
> René Oudeweg
>