Additional Information

Table of Contents


We provide additional information concerning Mycelium and how to properly use it.

Connect to Other Nodes

If you want to connect to other nodes, you can specify their listening address as part of the command (combined with the protocol they are listening on, usually TCP);

mycelium --peers tcp:// quic://

If you are using other tun inferface, e.g. utun3 (default), you can set a different utun inferface

mycelium --peers tcp:// quic:// --tun-name utun9

Possible Peers

Here are some possible peers.


Default Port

By default, the node will listen on port 9651, though this can be overwritten with the -p flag.

Check Network Information

You can check your Mycelium network information by running the following line:

mycelium inspect --json

Where a typical output would be:

  "publicKey": "abd16194646defe7ad2318a0f0a69eb2e3fe939c3b0b51cf0bb88bb8028ecd1d",
  "address": "3c4:c176:bf44:b2ab:5e7e:f6a:b7e2:11ca"

Test the Network

You can easily test that the network works by pinging to anyone in the network.

ping6 3c4:c176:bf44:b2ab:5e7e:f6a:b7e2:11ca

Key Pair

The node uses a x25519 key pair from which its identity is derived. The private key of this key pair is saved in a local file (32 bytes in binary format). You can specify the path to this file with the -k flag. By default, the file is saved in the current working directory as priv_key.bin.

Running without TUN interface

It is possible to run the system without creating a TUN interface, by starting with the --no-tun flag. Obviously, this means that your node won't be able to send or receive L3 traffic. There is no interface to send packets on, and consequently no interface to send received packets out of. From the point of other nodes, your node will simply drop all incoming L3 traffic destined for it. The node will still route traffic as normal. It takes part in routing, exchanges route info, and forwards packets not intended for itself.

The node also still allows access to the message subsystem.


The node starts an HTTP API, which by default listens on localhost:8989. A different listening address can be specified on the CLI when starting the system through the --api-server-addr flag. The API allows access to send and receive messages, and will later be expanded to allow admin functionality on the system. Note that message are sent using the identity of the node, and a future admin API can be used to change the system behavior. As such, care should be taken that this API is not accessible to unauthorized users.

Message System

A message system is provided which allows users to send a message, which is essentially just "some data" to a remote. Since the system is end-to-end encrypted, a receiver of a message is sure of the authenticity and confidentiality of the content. The system does not interpret the data in any way and handles it as an opaque block of bytes. Messages are sent with a deadline. This means the system continuously tries to send (part of) the message, until it either succeeds, or the deadline expires. This happens similar to the way TCP handles data. Messages are transmitted in chunks, which are embedded in the same data stream used by L3 packets. As such, intermediate nodes can't distinguish between regular L3 and message data.

The primary way to interact with the message system is through the API. The message API is documented in here. For some more info about how to use the message system, see the Message section.

Inspecting Node Keys

Using the inspect subcommand, you can view the address associated with a public key. If no public key is provided, the node will show its own public key. In either case, the derived address is also printed. You can specify the path to the private key with the -k flag. If the file does not exist, a new private key will be generated. The optional --json flag can be used to print the information in json format.

mycelium inspect a47c1d6f2a15b2c670d3a88fbe0aeb301ced12f7bcb4c8e3aa877b20f8559c02

Where the output could be something like this:

Public key: a47c1d6f2a15b2c670d3a88fbe0aeb301ced12f7bcb4c8e3aa877b20f8559c02
Address: 27f:b2c5:a944:4dad:9cb1:da4:8bf7:7e65
Last change: 2024-02-27