# Interacting with the Node

There are multiple ways to interact with a node: using the CLI, using gRPC or using the REST endpoints.

# Pre-requisite Readings

# Using the CLI

Now that your chain is running, it is time to try sending tokens from the first account you created to a second account. In a new terminal window, start by running the following query command:

Copy simd query bank balances $MY_VALIDATOR_ADDRESS --chain-id my-test-chain

You should see the current balance of the account you created, equal to the original balance of stake you granted it minus the amount you delegated via the gentx. Now, create a second account:

Copy simd keys add recipient --keyring-backend test # Put the generated address in a variable for later use. RECIPIENT=$(simd keys show recipient -a --keyring-backend test)

The command above creates a local key-pair that is not yet registered on the chain. An account is created the first time it receives tokens from another account. Now, run the following command to send tokens to the recipient account:

Copy simd tx bank send $MY_VALIDATOR_ADDRESS $RECIPIENT 1000000stake --chain-id my-test-chain --keyring-backend test # Check that the recipient account did receive the tokens. simd query bank balances $RECIPIENT --chain-id my-test-chain

Finally, delegate some of the stake tokens sent to the recipient account to the validator:

Copy simd tx staking delegate $(simd keys show my_validator --bech val -a --keyring-backend test) 500stake --from recipient --chain-id my-test-chain --keyring-backend test # Query the total delegations to `validator`. simd query staking delegations-to $(simd keys show my_validator --bech val -a --keyring-backend test) --chain-id my-test-chain

You should see two delegations, the first one made from the gentx, and the second one you just performed from the recipient account.

# Using gRPC

The Protobuf ecosystem developed tools for different use cases, including code-generation from *.proto files into various languages. These tools allow the building of clients easily. Often, the client connection (i.e. the transport) can be plugged and replaced very easily. Let's explore one of the most popular transport: gRPC.

Since the code generation library largely depends on your own tech stack, we will only present three alternatives:

  • grpcurl for generic debugging and testing,
  • programmatically via Go,
  • CosmJS for JavaScript/TypeScript developers.

# grpcurl

grpcurl (opens new window) is like curl but for gRPC. It is also available as a Go library, but we will use it only as a CLI command for debugging and testing purposes. Follow the instructions in the previous link to install it.

Assuming you have a local node running (either a localnet, or connected a live network), you should be able to run the following command to list the Protobuf services available (you can replace localhost:9000 by the gRPC server endpoint of another node, which is configured under the grpc.address field inside app.toml):

Copy grpcurl -plaintext localhost:9090 list

You should see a list of gRPC services, like cosmos.bank.v1beta1.Query. This is called reflection, which is a Protobuf endpoint returning a description of all available endpoints. Each of these represents a different Protobuf service, and each service exposes multiple RPC methods you can query against.

In order to get a description of the service you can run the following command:

Copy grpcurl \ localhost:9090 \ describe cosmos.bank.v1beta1.Query # Service we want to inspect

It's also possible to execute an RPC call to query the node for information:

Copy grpcurl \ -plaintext -d '{"address":"$MY_VALIDATOR"}' \ localhost:9090 \ cosmos.bank.v1beta1.Query/AllBalances

The list of all available gRPC query endpoints is coming soon (opens new window).

# Query for historical state using grpcurl

You may also query for historical data by passing some gRPC metadata (opens new window) to the query: the x-cosmos-block-height metadata should contain the block to query. Using grpcurl as above, the command looks like:

Copy grpcurl \ -plaintext \ -H "x-cosmos-block-height: 279256" \ -d '{"address":"$MY_VALIDATOR"}' \ localhost:9090 \ cosmos.bank.v1beta1.Query/AllBalances

Assuming the state at that block has not yet been pruned by the node, this query should return a non-empty response.

# Programmatically via Go

The following snippet shows how to query the state using gRPC inside a Go program. The idea is to create a gRPC connection, and use the Protobuf-generated client code to query the gRPC server.

Copy import ( "context" "fmt" "google.golang.org/grpc" sdk "github.com/cosmos/cosmos-sdk/types" "github.com/cosmos/cosmos-sdk/types/tx" ) func queryState() error { myAddress, err := sdk.AccAddressFromBech32("cosmos1...") if err != nil { return err } // Create a connection to the gRPC server. grpcConn := grpc.Dial( "", // your gRPC server address. grpc.WithInsecure(), // The SDK doesn't support any transport security mechanism. ) defer grpcConn.Close() // This creates a gRPC client to query the x/bank service. bankClient := banktypes.NewQueryClient(grpcConn) bankRes, err := bankClient.Balance( context.Background(), &banktypes.QueryBalanceRequest{Address: myAddress, Denom: "atom"}, ) if err != nil { return err } fmt.Println(bankRes.GetBalance()) // Prints the account balance return nil }

You can replace the query client (here we are using x/bank's) with one generated from any other Protobuf service. The list of all available gRPC query endpoints is coming soon (opens new window).

# Query for historical state using Go

Querying for historical blocks is done by adding the block height metadata in the gRPC request.

Copy import ( "context" "fmt" "google.golang.org/grpc" "google.golang.org/grpc/metadata" grpctypes "github.com/cosmos/cosmos-sdk/types/grpc" "github.com/cosmos/cosmos-sdk/types/tx" ) func queryState() error { // --snip-- var header metadata.MD bankRes, err = bankClient.Balance( metadata.AppendToOutgoingContext(context.Background(), grpctypes.GRPCBlockHeightHeader, "12"), // Add metadata to request &banktypes.QueryBalanceRequest{Address: myAddress, Denom: denom}, grpc.Header(&header), // Retrieve header from response ) if err != nil { return err } blockHeight = header.Get(grpctypes.GRPCBlockHeightHeader) fmt.Println(blockHeight) // Prints the block height (12) return nil }

# CosmJS

CosmJS documentation can be found at https://cosmos.github.io/cosmjs (opens new window). As of January 2021, CosmJS documentation is still work in progress.

# Using the REST Endpoints

As described in the gRPC guide, all gRPC services on the Cosmos SDK are made available for more convenient REST-based queries through gRPC-gateway. The format of the URL path is based on the Protobuf service method's full-qualified name, but may contain small customizations so that final URLs look more idiomatic. For example, the REST endpoint for the cosmos.bank.v1beta1.Query/AllBalances method is GET /cosmos/bank/v1beta1/balances/{address}. Request arguments are passed as query parameters.

As a concrete example, the curl command to make balances request is:

Copy curl \ -X GET \ -H "Content-Type: application/json" \ http://localhost:1317/cosmos/bank/v1beta1/balances/$MY_VALIDATOR

Make sure to replace localhost:1317 with the REST endpoint of your node, configured under the api.address field.

The list of all available REST endpoints is available as a Swagger specification file, it can be viewed at localhost:1317/swagger. Make sure that the api.swagger field is set to true in your app.toml file.

# Query for historical state using REST

Querying for historical state is done using the HTTP header x-cosmos-block-height. For example, a curl command would look like:

Copy curl \ -X GET \ -H "Content-Type: application/json" \ -H "x-cosmos-block-height: 279256" http://localhost:1317/cosmos/bank/v1beta1/balances/$MY_VALIDATOR

Assuming the state at that block has not yet been pruned by the node, this query should return a non-empty response.

# Cross-Origin Resource Sharing (CORS)

CORS policies (opens new window) are not enabled by default to help with security. If you would like to use the rest-server in a public environment we recommend you provide a reverse proxy, this can be done with nginx (opens new window). For testing and development purposes there is an enabled-unsafe-cors field inside app.toml.

# Next

Sending transactions using gRPC and REST requires some additional steps: generating the transaction, signing it, and finally broadcasting it. Read about generating and signing transactions.