TxMEx

Transaction Message Exchange (TxMEx) is a service for Bitcore that allows to send and receive messages between the nodes of a Bitcoin network

Requirements

• bitcore-node
• bitcore-lib
• bitcore-explorers
• insight-api

Set-up

If you already have a running Bitcore node, you can skip directly to TxMEx

Bitcore

To install a Bitcore Full Node, you should refer to https://bitcore.io/guides/full-node/
This is a short guide to install it on Debian-based OSs:

• Install NVM: wget https://raw.githubusercontent.com/creationix/nvm/v0.33.1/install.sh | bash
• Install Node 4: nvm install 4
• Install Requirements: apt-get install npm libzmq3-dev build-essential curl
• Install Bitcore: npm install -g bitcore
• Create your Bitcore full node: bitcore create [--testnet] MY_NODE

TxMEx

• From your node folder: bitcore install insight-api txmex

Usage

In order to interact with the TxMEx (for short, TM) service, you can use the 'bitcore call' API command.

The available commands are:

• getnetstatus: returns nodes in the default TM network
• createnode: creates a new TM node;
  • SYNTAX: 'createnode NAME' ; if NAME=auto, the name will be choose automatically; if NAME=temp, the node won't be saved
• addnode: adds an existing Bitcoin node to the TM network;
  • SYNTAX: 'addnode NAME PRIV_KEY' ; NAME follows the same rules as in 'createnode'
• removenode: removes a node from the TM network;
  • SYNTAX: 'removenode NAME'
• getnodestatus: returns funds and in/out messages for a TM node;
  • SYNTAX: 'getnodestatus NAME'
• sendmessage: sends a message from one TM node to another;
  • SYNTAX: 'sendmessage SRC_ID DST_{NAME|ADDR} MESSAGE'
• getmessages: retrieves all TM messages for a TM node;
  • SYNTAX: 'getmessages ID'
• waitmessage: wait for a new TM message for the local TM network;
  • SYNTAX: 'waitmessage'
• waitmessagefrom: wait for a new TM message from a specific source address;
  • SYNTAX: 'waitmessagefrom {ID|ADDR}'
• waitmessageto: wait for a new TM message to a specific source address;
  • SYNTAX: 'waitmessageto ID'

TxMEx protocol details

Messages are splitted into chunks of 76 bytes, each of which is embedded into a transaction, through the OP_RETURN Script command. Each transaction sends 546 satoshis (the minimum valid amount), and adds a fee of 3000 (a little higher than the minimum required by Bitcore).

The format of the message is:

| 'TM' | len | seq | message_chunk |
|. 0-1 .| . 2 . | . 3 . | ......... 4-79 ......... |

Once the TxMEx service recieves all chunks of a message it assembles them and notify the TM network with a 'bus event'. The destination node will read the message and optionally take some actions. The first 3 characters of the message are interpreted as a command. Currently, only 2 commands are considered: 'png' and 'ack'; when a node receives a 'png' command, it will send back an 'ack' message.
[In a future release, nodes will have the ability to load a 'rule set', defining their behavior]

Limitations

• TxMEx does not encrypt private key, so they are currently stored in clear on the hard drive
• Nodes need funds to send messages. [It is planned to add an automatic faucet request, for Testnet]
• TxMEx currently support one network per-node [TxMEx design has been thought for multiple networks, so this limitation will be removed soon]