In this section we will guide you through deploying an application on top of Babble using the socket interface. Babble comes with the Dummy application which is used in this demonstration. It is a simple chat application where users write messages on a channel and Babble guarantees that everyone sees the same messages in the same order.


We have provided a series of scripts to bootstrap a demo. Let us first use the easy method to view the demo and then we will take a closer look at what is happening behind the scenes.

Make sure you have Docker installed.

The demo will pull Docker images from our official public Docker registry

[...]/babble$ cd demo
[...]/babble/demo$ make

Once the testnet is started, a script is automatically launched to monitor consensus figures:

consensus_events:180 consensus_transactions:40 events_per_second:0.00 id:1 last_block_index:3 last_consensus_round:17 num_peers:3 round_events:7 rounds_per_second:0.00 state:Babbling sync_rate:1.00 transaction_pool:0 undetermined_events:18
consensus_events:180 consensus_transactions:40 events_per_second:0.00 id:3 last_block_index:3 last_consensus_round:17 num_peers:3 round_events:7 rounds_per_second:0.00 state:Babbling sync_rate:1.00 transaction_pool:0 undetermined_events:20
consensus_events:180 consensus_transactions:40 events_per_second:0.00 id:2 last_block_index:3 last_consensus_round:17 num_peers:3 round_events:7 rounds_per_second:0.00 state:Babbling sync_rate:1.00 transaction_pool:0 undetermined_events:21
consensus_events:180 consensus_transactions:40 events_per_second:0.00 id:0 last_block_index:3 last_consensus_round:17 num_peers:3 round_events:7 rounds_per_second:0.00 state:Babbling sync_rate:1.00 transaction_pool:0 undetermined_events:20

Running docker ps -a will show you that 9 docker containers have been launched:

[...]/babble/demo$ docker ps -a
CONTAINER ID        IMAGE                    COMMAND                  CREATED             STATUS              PORTS                   NAMES
ba80ef275f22        mosaicnetworks/watcher   "/"              48 seconds ago      Up 7 seconds                                watcher
4620ed62a67d        mosaicnetworks/dummy     "dummy '--name=client"   49 seconds ago      Up 48 seconds       1339/tcp                client4
847ea77bd7fc        mosaicnetworks/babble    "babble run --cache_s"   50 seconds ago      Up 49 seconds       80/tcp, 1337-1338/tcp   node4
11df03bf9690        mosaicnetworks/dummy     "dummy '--name=client"   51 seconds ago      Up 50 seconds       1339/tcp                client3
00af002747ca        mosaicnetworks/babble    "babble run --cache_s"   52 seconds ago      Up 50 seconds       80/tcp, 1337-1338/tcp   node3
b2011d3d65bb        mosaicnetworks/dummy     "dummy '--name=client"   53 seconds ago      Up 51 seconds       1339/tcp                client2
e953b50bc1db        mosaicnetworks/babble    "babble run --cache_s"   53 seconds ago      Up 52 seconds       80/tcp, 1337-1338/tcp   node2
0c9dd65de193        mosaicnetworks/dummy     "dummy '--name=client"   54 seconds ago      Up 53 seconds       1339/tcp                client1
d1f4e5008d4d        mosaicnetworks/babble    "babble run --cache_s"   55 seconds ago      Up 54 seconds       80/tcp, 1337-1338/tcp   node1

Indeed, each node is comprised of an App and a Babble node (cf Design section). The watcher container monitors consensus figures.

Run the demo script to play with the Dummy App which is a simple chat application powered by the Babble consensus platform:

[...]/babble/demo$ make demo

Finally, stop the testnet:

[...]/babble/demo$ make stop

Manual Setup

The above scripts hide a lot of the work required for setting up a Babble network. They generate the configuration files automatically, copy them to the right places and launch the nodes in Docker containers. We recommend looking at these scripts closely to understand how the demo works. Here, we will attempt to explain the individual steps that take place behind the scenes.


Babble reads configuration from the directory specified by the datadir flag which defaults to ~/.babble on UNIX systems. This directory should contain the following files:

  • priv_key : The private key of the validator runnning the node.
  • peers.json : The current validator-set.
  • genesis.peers.json : (optional, default peers.json) The initial validator-set of the network.


Every participant has a cryptographic key-pair that it uses to encrypt, sign and verify messages. The private key is secret but the public key is used by other nodes to verify messages signed with the private key.

The encryption scheme used by Babble is ECDSA with the secp256k1 curve (like Bitcoin and Ethereum).

Babble’s keygen command can be used to generate key-pairs in the appropriate format.


peers.json and genesis.peers.json are used to determine the current and initial validator-sets of a network.

genesis.peers.json corresponds to the initial validator-set; the one that the hashgraph was started with. If genesis.peers.json is not provided, Babble will use peers.json as the genesis validator-set.

peers.json corresponds to the current validator-set. These are the nodes that are allowed to record new Events in the hashgraph, and who will gossip among each other.

peers.json and gensesis.peers.json are not necessarily equal because the dynamic membership protocol enables new nodes to join or leave a live Babble network dynamically. It is important for a joining node to know the initial validator-set in order to replay and verify the hashgraph up to the point where it joins.

It is possible to start a Babble network with just a single node, or with a predefined validator-set composed of multiple nodes.

In the latter case, someone, or some process, needs to aggregate the public keys and network addresses of all participants into a single file (peers.genesisjson), and ensure that everyone has a copy of this file. It is left to the user to derive a scheme to produce the configuration files but the docker demo scripts are a good place to start.


Let us say I want to participate in a Babble network. I am going to start by running babble keygen to create a key-pair:

babble keygen
Your private key has been saved to: /home/[user]/.babble/priv_key
Your public key has been saved to: /home/[user]/.babble/

Next, I am going to copy the public key ( and communicate it to whoever is responsible for producing the peers.json file. At the same time, I will tell them that I am going to be listening on You may also optionally supply a moniker for each node, which is far more readable than a public key address.

Suppose three other people do the same thing. The resulting peers.json file could look something like this:


Now everyone is going to take a copy of this peers.json file and put it in a folder together with the priv_key file they generated in the previous step. That is the folder that they need to specify as the datadir when they run Babble.

Babble Executable

Let us take a look at the help provided by the Babble CLI:

Run node

  babble run [flags]

  -a, --advertise string          Advertise IP:Port for babble node
      --bootstrap                 Load from database
      --cache-size int            Number of items in LRU caches (default 10000)
  -c, --client-connect string     IP:Port to connect to client (default "")
      --datadir string            Top-level directory for configuration and data (default "/home/martin/.babble")
      --db string                 Dabatabase directory (default "/home/martin/.babble/badger_db")
      --fast-sync                 Enable FastSync
      --heartbeat duration        Timer frequency when there is something to gossip about (default 10ms)
  -h, --help                      help for run
  -j, --join-timeout duration     Join Timeout (default 10s)
  -l, --listen string             Listen IP:Port for babble node (default "")
      --log string                debug, info, warn, error, fatal, panic (default "debug")
  -R, --maintenance-mode          Start Babble in a suspended (non-gossipping) state
      --max-pool int              Connection pool size max (default 2)
      --moniker string            Optional name
      --no-service                Disable HTTP service
  -p, --proxy-listen string       Listen IP:Port for babble proxy (default "")
  -s, --service-listen string     Listen IP:Port for HTTP service (default "")
      --signal-addr string        IP:Port of WebRTC signaling server (default "")
      --signal-skip-verify        (Insecure) Accept any certificate presented by the signal server
      --slow-heartbeat duration   Timer frequency when there is nothing to gossip about (default 1s)
      --store                     Use badgerDB instead of in-mem DB
      --suspend-limit int         Limit of undetermined events (per node) before entering suspended state (default 100)
      --sync-limit int            Max number of events for sync (default 1000)
  -t, --timeout duration          TCP Timeout (default 1s)
      --webrtc                    Use WebRTC transport

The listen flag controls the local address:port where this node gossips with other nodes. If the node is running behind some kind of NAT, it is possilbe to advertise a different address with the advertise flag. If advertise is not specified, the node defaults to using the listen address. By default listen is, meaning that Babble will bind to the loopback addresse on the local machine.

As we explained in the architecture section, each Babble node works in conjunction with an application for which it orders transactions. When Babble and the application are connected by a TCP interface, we specify two other endpoints:

  • proxy-listen : where Babble listens for transactions from the App
  • client-connect : where the App listens for transactions from Babble

We can also specify where Babble exposes its HTTP API providing information on the Hashgraph and Blockchain data store. This is controlled by the optional service-listen flag.

The fast-sync parameter determines whether or not the node will attempt to fast-forward to the tip of the hashgraph, or download and replay the entire hashgraph from start. More on this in fast-sync

We can choose to run Babble with a database backend or only with an in-memory cache. With the store flag set, Babble will look for a database file in datadir/babdger_db or in the path specified by db. If the database already exists, and the --boostrap flag is set, the node will load the database and bootstrap itself to a state consistent with the database and it will be able to proceed with the consensus algorithm from there. If the database does not exist yet, or the --bootstrap flag is not set, a new one will be created and the node will start from a clean state.

The node can also be started in maintenance-mode with the homonymous flag. The node is started normally but goes straight into the Suspended state, where it still responds to sync-requests, and service API requests, but does not produce or insert new Events in the underlying hashgraph. The Suspended state is also triggered automatically when more than suspend-limit undetermined-events were created since last starting the node. This is a safeguard against runaway conditions when a network does not have a strong majority and produces undetermined-events ad infinitum.

Here is how the Docker demo starts Babble nodes together wth the Dummy application:

for i in $(seq 1 $N)
    docker run -d --name=client$i --net=babblenet --ip=172.77.10.$i -it mosaicnetworks/dummy:latest \
    --name="client $i" \
    --client-listen="172.77.10.$i:1339" \
    --proxy-connect="172.77.5.$i:1338" \
    --discard \

for i in $(seq 1 $N)
    docker create --name=node$i --net=babblenet --ip=172.77.5.$i mosaicnetworks/babble:latest run \
    --heartbeat=100ms \
    --moniker="node$i" \
    --cache-size=50000 \
    --listen="172.77.5.$i:1337" \
    --proxy-listen="172.77.5.$i:1338" \
    --client-connect="172.77.10.$i:1339" \
    --service-listen="172.77.5.$i:80" \
    --sync-limit=500 \
    --fast-sync=$FASTSYNC \
    --store \

    docker cp $MPWD/conf/node$i node$i:/.babble
    docker start node$i

Stats, blocks and Logs

Once a node is up and running, we can call the stats endpoint exposed by the HTTP service:

curl -s

Or request to see a specific block:

curl -s

Or we can look at the logs produced by Babble:

docker logs node1

We can look at the current state of docker containers:

docker ps --all