grin/doc/local_net.md

Grin Local Testing Network

Basic Execution

For a basic example simulating a single node network, create a directory called node1 and change your working directory to it. You'll use this directory to run a wallet and create a new blockchain via a server running in mining mode.

You'll need a config file - the easiest is to copy over the grin.toml file from the root grin directory into the node1 directory you just made.

Before running your mining server, a wallet server needs to be set up and listening so that the mining server knows where to send mining rewards. This can all be configured in the grin.toml file. We will use the defaults, with the wallet listener automatically started on port 13415.

See wallet for more info on the various Grin wallet commands and options.

Next enable the test miner with the following change to your grin.toml file:

#Whether to run a test miner. This is only for developer testing (chaintype
#usertesting) at cuckoo 16, and will only mine into the default wallet port.
run_test_miner = true

Also make sure to uncomment the following line, or else the mined coins will be burned:

test_miner_wallet_url = "http://127.0.0.1:13415"

Now, start up the grin server:

node1$ grin server run

This creates a new .grin database directory in the current directory, and begins mining new blocks (with no transactions, for now). Note this starts two services listening on two default ports:

• 13414 for the peer-to-peer (P2P) service which keeps all nodes synchronized
• 13413 for the Rest API service used to verify transactions and post new transactions to the pool (for example)

These ports can be configured via command line switches, or via a grin.toml file in the working directory.

Let the mining server find a few blocks, then stop (just ctrl-c) the grin server. You'll notice grin has created a database directory (.grin) in which the blockchain and peer data is stored. There should also be a wallet.dat file in the current directory, which contains a few coinbase mining rewards created each time the server mines a new block.

Alternatively, if mining at Cuckoo 30 is desired, you can utilize the grin-miner instead of the test miner (Cuckoo 16). After starting the grin server, open another terminal, navigate to the grin-miner directory, and start up the grin miner (we will again use the default configuration):

grin-miner$ grin-miner

Advanced Example

The following outlines a more advanced example simulating a multi-server network with transactions being posted.

For the sake of example, we're going to run three nodes with varying setups. Create two more directories beside your node1 directory, called node2 and node3 and copy over the grin.toml file from the root into each directory.

There are a few configurations we will change for all three nodes:

#UserTesting - For regular user testing (cuckoo 16)
chain_type = "UserTesting"

#flag whether stratum server is enabled
enable_stratum_server = false

If you want to clear data from your previous run (or anytime you want to reset the blockchain and all peer data) just delete the wallet.dat file in the node1 directory and run rm -rf .grin to remove grin's database.

Node 1: Genesis and Miner

As before, node 1 will create the blockchain and begin mining. As we'll be running many servers from the same machine, we'll configure specific ports for other servers to explicitly connect to.

First, we'll edit our grin.toml file to receive rewards on port 15000.

# Port for wallet listener
api_listen_port = 15000

# Where the wallet should find a running node
check_node_api_http_addr = "http://localhost:10001"

We will also turn on the test miner and designate a wallet url for mined coinbase rewards. Again in the grin.toml change the following:

#Whether to run a test miner. This is only for developer testing (chaintype
#usertesting) at cuckoo 16, and will only mine into the default wallet port.
run_test_miner = true

#test miner wallet URL (burns if this doesn't exist)
test_miner_wallet_url = "http://127.0.0.1:15000"

#the wallet receiver to which coinbase rewards will be sent
wallet_listener_url = "http://127.0.0.1:15000"

Then we start node 1 mining with its P2P server bound to port 10000 and its api server at 10001.

node1$ grin server -p 10000 -a 10001 run

Node 2: Regular Node (not mining)

We'll set up Node 2 as a simple validating node (i.e. it won't mine but we'll pass in the address of node 1 as a seed). Therefore, we can turn off the wallet listener by making the following change to grin.toml (on by default):

#Whether to run the wallet listener with the server by default
run_wallet_listener = false

Node 2 will join the network founded by node 1 and then sync its blockchain and peer data. In a new terminal, tell node 2 to run a server using node 1's P2P address as a seed. Node 2's P2P server will run on port 20000 and its API server will run on port 20001.

node2$ grin server -s "127.0.0.1:10000" -p 20000 -a 20001 run

Node 2 will then sync, processing and validating new blocks that node 1 may find.

Node 3: Regular node running wallet listener

Similar to Node 2, we'll set up node 3 as a non-mining node seeded with node 2 (node 1 could also be used). We'll also run another wallet in listener mode on this node and specify the port as we did for node 1:

# Port for wallet listener
api_listen_port = 35000

# Where the wallet should find a running node
check_node_api_http_addr = "http://localhost:30001"

We'll specify the port as we did for node 1 and start up node 3:

node3$ grin server -s "127.0.0.1:20000" -p 30000 -a 30001 run

Node 3 is now running it's P2P service on port 30000 and its API server on 30001. You should be able to see it syncing its blockchain and peer data with nodes 1 and 2.

In contrast to other blockchains, a feature of a MimbleWimble is that a transaction cannot just be directly posted to the blockchain. It first needs to be sent from the sender to the receiver, who will add a blinding factor before posting it to the blockchain. The above command tells the wallet server to listen for transactions on port 35000, and, after applying it's own blinding factor to the transaction, forward them on to the listening API server on node 1. (NB: we should theoretically be able to post transactions to node 3 or 2, but for some reason transactions posted to peers don't seem to propagate properly at present)

Send grins from node 1 to node 3

With all of your servers happily running and your terminals scrolling away, let's spend some of the coins mined in node 1 by sending them to node 3's listening wallet.

In yet another terminal in node 1's directory, create a new partial transaction spending 10 coins and send them on to node 3's wallet listener. We'll also specify that we'll use node 2's API listener to validate our transaction inputs before sending:

node1$ grin wallet -a "http://127.0.0.1:20001" send 10 -d "http://127.0.0.1:35000"

Your terminal windows should all light up now. Node 1 will check its inputs against node 2, and then send a partial transaction to node 3's wallet listener. Node 3 has been configured to send signed and finalized transactions to the api listener on node 1, which should then add the transaction to the next block and validate it via mining.

To check how many confirmations your transaction has received, change back to the terminal running node 3 and type the following:

node3$ grin wallet -a "http://127.0.0.1:30001" outputs

You can feel free to try any number of permutations or combinations of the above, just note that grin is very new and under active development, so your mileage may vary. You can also simplify these command line switches by further editing the grin.toml file in each server's directory.