This mrefd repository builds a new kind of M17 open-source Reflector. Although mrefd has evolved, most of the code is originally based on groundbreaking development of XLXD and the copyrights of all relevant source files reflect this. The sources are published under GPL Licenses.

The mrefd reflector is for connecting M17 clients together. mrefd can be configured with up to 26 different channels. M17 clients (M17 repeaters, M17 hot-spots and other MREFD reflectors) can be linked to a channel. An incoming M17 voice stream from one of the clients will be heard by all the other clients.

Encrypted voice streams will pass through an mrefd channel, but only if they are configured for it.

mrefd uses Ham-DHT, a distributed hash table network for sharing digital information for ham radio. A Ham-DHT-enabled mrefd publishes a four-part document on the DHT network. The four parts:

1. Configuration - Connecting clients can use this to know how to connect.
2. Peers - Other mrefd reflectors that are interlinked is in this part.
3. Clients - Any node listing to any configured module is in this part. This includes simple clients as well as other interlinked reflector modules.
4. Last heard users - A limited list of last heard users is in this part. Any node on the network can read an mrefd document. The key to the mrefd document is the reflector's callsign. either the entire document or any part of the document may be retrieved.

The dashboard for mrefd is available here.

Only systemd-based operating systems are supported. Debian or Ubuntu is recommended. If you want to install this on a non-systemd based OS, you are on your own. This repository is designed so that you don't have to modify any file in the repository when you build your system. Any file you need to modify to properly configure your reflector will be a file you copy from you locally cloned repo. This makes it easier to update the source code when this repository is updated. Follow the instructions below to build your M17 reflector.

A client callsign must begin with something that looks like a legal callsign: it begins with an optional digit, followed by one or two letters followed by one or two digit, followed by one to four letters. After that, any valid M17 characters can appear as a suffix as long as the first of these suffix characters is a non-alphanumeric M17 character, i.e., a space (' '), period ('.'), slash ('/') or dash ('-').

The packages which are described in this document are designed to install server software which is used for the digital voice network infrastructure. It requires a 24/7 internet connection which can support 20 voice streams or more to connect repeaters and hot-spots and other digital voice clients!

• The server can build a reflector that support IPv4, IPv6 or both (dual stack).
• The public IP addresses should have a DNS record which must be published in the common host files.

Below are instructions for building an mrefd reflector.

sudo apt update
sudo apt upgrade

sudo apt install git build-essential g++ libcurl4-gnutls-dev

The libcurl4-gnutls-dev package is only necessary if you use OpenDHT. OpenDHT and gomrefdash both have their own requirements.

Ham-DHT is implemented using a distributed hash table provided by OpenDHT.

OpenDHT is available here. Building and installing instructions are in the OpenDHT Wiki. Python support and proxy-server support (RESTinio) is not required for mrefd and so can be considered optional. With this in mind, this should work on Debian/Ubuntu-based systems:

# Install OpenDHT dependencies
sudo apt install libncurses5-dev libreadline-dev nettle-dev libgnutls28-dev libargon2-0-dev libmsgpack-dev  libssl-dev libfmt-dev libjsoncpp-dev libhttp-parser-dev libasio-dev cmake pkg-config libcppunit-dev

# clone the repo
git clone https://github.com/savoirfairelinux/opendht.git

# build and install
cd opendht
mkdir build && cd build
cmake -DOPENDHT_PYTHON=OFF -DCMAKE_INSTALL_PREFIX=/usr ..
make
sudo make install

Please note that there is no easy way to uninstall OpenDHT once it's been installed.

git clone https://github.com/n7tae/mrefd.git
cd mrefd

cp config/mrefd.blacklist .
cp config/mrefd.whitelist .
cp config/mrefd.interlink .

Use your favorite editor to modify each of these files. If you want a totally open network, the blacklist and whitelist files are ready to go. The blacklist determine which callsigns can't use the reflector. The whitelist determines which callsigns can use the reflector. The mrefd reflector will monitor these file and dynamically update itself whenever anything changes. There is no need to stop and restart the reflector.

The mrefd.interlink file sets up the M17<--->M17 peer group linking. Please read the comments in this file. An M17 interlink now has to be configured on both sides of the link. Linked reflectors can share multiple modules, but cross module linking, for example, linking M17-000 module A to M17-001 module B is not supported. Using the Ham-DHT greatly simplifies setting up a peer group. You don't have to specify an IP address or port number as the Ham-DHT will provided it, and this information comes directly from the peer. Using the Ham-DHT will prevent you from interlinking a channel where the peer channel has encryption enabled and you do not, or vis versa.

If your reflector or your desired peer doesn't use Ham-DHT, you can specify the IP address and port in the mrefd.interlink file. It will be then up to the reflector admins to make sure the encryption configurations match.

Inter-linking a channel to more than one other reflector demands all reflector in a group are linked to all other reflectors in the group. This will result in the shortest possible latency between a client and any other client on the group. This XLX-like mode of linking is enforced by implementing a one hop policy where a voice stream is marked by a reflector when it is passed to another reflector. The receiving reflector will then know not to pass the voice stream on to any other reflector.

Group administration will require coordination among the admins of all involved reflectors. If a group member drops out or if a new member wants to join a group, all other group members will need to remove or add a line to their mrefd.interlink file.

Configuring, compiling and maintaining your reflector build is easy! Start by copying the configuration example files:

cp example.mk mrefd.mk     # this  file  sets the compile-time configuration
cp example.cfg mrefd.cfg   # while this file sets the run-time configuration

Use your favorite editor to edit mrefd.mk and mrefd.cfg. These file contains comments so it should be obvious what values need changing.

After you have written your configuration files, you can build and install your system:

make && sudo make install

Use this command to compile and install your system. Use sudo make uninstall to uninstall mrefd.

To stop the execution of mrefd:

sudo systemctl stop mrefd

You can start mrefd by replacing stop with start, or you can restart it by using restart.

To view the mrefd log:

sudo journalctl -u mrefd -f

The blacklist, whitelist and interlink files can be modified in real time while xrfd is executing and the reflector will update itself within a few seconds. If USESYMLINK is true in your mrefd.mk file, then you can edit the files in your build directory. Otherwise, you will need to edit the files in the CFGDIR folder.

The official M17 dashboard is in another repo.

git clone https://github.com/kc1awv/gomrefdash.git

This a a dashboard based on the go programming language. If you don't have it, you will need to install it first. Follow the instructions on that repo for getting your dashboard up and running.

Here is the safest way to update your reflector:

sudo make uninstall
make clean
git pull
make
sudo make install

If, after doing the git pull, you see that it's downloaded a new example.cfg file, it would probably be a good idea to remake your mrefd.cfg file. There may be new options of which you might want to take advantage.

It should be fairly straightforward to install multiple mrefd instances on a single server. Make sure each instance is using a different listening port. Things to me aware of:

• The reflector executable name is defined in the Makefile at the line "EXE=mrefd".
• The configuration file is read at start-up and defined in mrefd.service file. Each instance would require a different service file.
• Each instance will need its own config files with unique paths to those files.
• Each instance will need a unique url so that each will have its own webpage.
• Need to add unix sockets for interlinking between instances.

This is not a task for a beginner!

MREFD requires the following port to be open to inbound network traffic:

• UDP port 17000 for M17
• UDP port 17171 for DHT
• TCP port 80 for HTTP
• TCP port 443 for HTTPS

• Copyright © 2020-2022 Thomas A. Early N7TAE