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In this section we will guide you through deploying an application on top of Babble. Babble comes with the Dummy application which is used in this demonstration. It is a simple chat application where participants 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 complications involved in 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 linux/osx. This directory must contain two files:

  • peers.json : Lists all the participants in the network.
  • priv_key.pem: Contains the private key of the validator runnning the node.

Every participant has a cryptographic key-pair that is used 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 P256 curve.

To run a Babble network, it is necessary to predefine who the participants are going to be. Each participant will generate a key-pair and decide which network address it is going to be using for the Babble protocol. Someone, or some process, then needs to aggregate the public keys and network addresses of all participants into a single file - the peers.json file. Every participant uses a copy of the same peers.json file. Babble will read that file to identify the participants in the network, communicate with them and verify their cryptographic signatures.

To generate key-pairs in a format usable by Babble, we have created the keygen command. 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.

So 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/martin/.babble/priv_key.pem
Your public key has been saved to: /home/martin/.babble/

The private key looks something like this:


and the corresponding public key looks like this:



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

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.pem 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]

      --cache-size int          Number of items in LRU caches (default 500)
  -c, --client-connect string   IP:Port to connect to client (default "")
      --datadir string          Top-level directory for configuration and data (default "/home/martin/.babble")
      --heartbeat duration      Time between gossips (default 1s)
  -h, --help                    help for run
  -l, --listen string           Listen IP:Port for babble node (default ":1337")
      --log string              debug, info, warn, error, fatal, panic
      --max-pool int            Connection pool size max (default 2)
  -p, --proxy-listen string     Listen IP:Port for babble proxy (default "")
  -s, --service-listen string   Listen IP:Port for HTTP service
      --standalone              Do not create a proxy
      --store                   Use badgerDB instead of in-mem DB
      --sync-limit int          Max number of events for sync (default 100)
  -t, --timeout duration        TCP Timeout (default 1s)

So we have just seen what the datadir flag does. The listen flag corresponds to the NetAddr in the peers.json file; that is the endpoint that Babble uses to communicate with other Babble nodes.

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.

Finally, 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. If the file exists, 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 file does not exist yet, it will be created and the node will start from a clean state.

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=172.77.5.$(($N+$i)) -it mosaicnetworks/dummy:0.4.0 \
    --name="client $i" \
    --client-listen="172.77.5.$(($N+$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.$i mosaicnetworks/babble:0.4.0 run \
    --cache-size=50000 \
    --timeout=200ms \
    --heartbeat=10ms \
    --listen="172.77.5.$i:1337" \
    --proxy-listen="172.77.5.$i:1338" \
    --client-connect="172.77.5.$(($N+$i)):1339" \
    --service-listen="172.77.5.$i:80" \
    --sync-limit=1000 \
    --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