Meshtastic Sniffer: decode nearby Meshtastic traffic with a cheap RTL-SDR

meshtastic-sniffer is a passive Meshtastic LoRa receiver written in C by cemaxecuter (CEMAXECUTER LLC, the DragonOS developer). It takes one wide slice of spectrum from a single software-defined radio and runs a LoRa decoder for every Meshtastic channel slot that fits inside it, all at once, without GNU Radio. Hackaday covered it on October 19, 2026: with DragonOS running and a HackRF One attached, it spotted his own node right away and showed its details in the terminal, and Hackaday suggests it for finding where conversations are happening, wardriving, and locating other networks. How much of the band you hear depends on the radio. The README says a HackRF One (20 MHz) covers roughly 73 to 80 US LongFast slots and the full EU_868 and EU_433 bands, a USRP B205mini or B210 at 26 Msps covers all of US 902-928 MHz, and an RTL-SDR dongle (2 MHz) covers about 8 LongFast slots. The cheapest way in is an RTL-SDR dongle such as the RTL-SDR Blog V3, run with --rtlsdr: it hears one band group, which is enough to see your own node and the traffic on a default LongFast channel. A HackRF One is the upgrade if you want most of the US band in one stare. It also supports BladeRF, SDRplay, Airspy, SoapySDR devices, VITA-49 network IQ and IQ file replay. With keys supplied, either the public default LongFast key or a channel-share URL from the Meshtastic app, it decrypts text, GPS, NodeInfo, telemetry and other standard ports. Frames that pass CRC are tagged as trusted, and decoded fields only appear when the key is known, the CRC passed and the payload parsed. Outputs include JSON, MQTT, ZMQ, CoT for ATAK, pcap, a daily archive and a web dashboard with live map, activity and topology tabs. Companion tools cover offline key recovery from captures, multi-station TDOA fusion and mobile wardriving with GPS. On DragonOS Noble the SDR libraries are already installed, so you clone, cmake and make; on Ubuntu or Debian you apt install the build tools and the libraries for your SDR first. The takeaway for everyone on a default channel: anyone with an SDR and this tool can read LongFast traffic, so use your own channel keys for anything private, and only decrypt traffic you are entitled to.