API access

You can connect to a Lotus node using the build in Lotus API. There is some preparation you need to do first on the node that you want to connect to. You must also generate an API key to use in order to connect to the Lotus node.

Enable remote API access

The Lotus Miner and the Lotus Node applications come with their own local API endpoints setup by default when they are running. Both lotus and lotus-miner act as a daemon (when launched with lotus daemon or lotus-miner run) and as client to that daemon (every other command).

In this section we will explain how to enable remote access to the Lotus APIs as run by the daemons.

Setting the listening interface

By default, the API listens on the local loopback interface 127.0.0.1. This is configured in the config.toml file:

To access the API remotely, Lotus needs to listen on the right IP/interface. The IP associated to each interface can be usually found with the command ip a. Once the right IP is known, it can be set in the configuration:

[API]
  ListenAddress = "/ip4/<EXTERNAL_INTERFACE_IP>/tcp/3453/http" # port is an example

  # Only relevant for lotus-miner
  RemoteListenAddress = "<EXTERNAL_IP_AS_SEEN_BY_OTHERS:<EXTERNAL_PORT_AS_SEEN_BY_OTHERS>"

0.0.0.0 can be used too. This is a wildcard that means “all interfaces”. Depending on the network setup, this may affect security (listening on the wrong, exposed interface).

After making these changes, please restart the affected process.

API tokens

Obtaining tokens

Any client wishing to talk to the API endpoints, exposed by either the Lotus Node or the Lotus Miner, will need a token. Tokens can be obtained as follows.

For the Lotus Node:

lotus auth create-token --perm <read,write,sign,admin>

For the Lotus Miner:

lotus-miner auth create-token --perm <read,write,sign,admin>

Note that the Lotus daemon and/or the Lotus Miner need to be running in the background!

Permissions

There are different permissions to choose from:

  • read - Read node state, no private data.
  • write - Write to local store / chain, and read permissions.
  • sign - Use private keys stored in wallet for signing, read and write permissions.
  • admin - Manage permissions, read, write, and sign permissions.

Default tokens

Notice how running lotus auth create-token is actually triggering a request to the API exposed by the Lotus daemon running in the background. This request is no different but the Lotus application (as client) is using a default pre-generated API token that is available locally and located in ~/.lotus/token.

The same applies for lotus-miner.

API client libraries

API clients take care of the low-level details of making requests and handling responses and let you focus on writing code specific to your project. They can also translate between different programming languages. These Filecoin API clients are currently available:

Go JSON-RPC client

To use the Lotus Go client, the Go RPC-API library can be used to interact with the Lotus API node. This library was written by Lotus developers and it is used by Lotus itself.

If your Lotus instance is hosted remotely, ensure that you have enabled remote API access. You will need to obtain an API token.

  1. First, import the necessary Go module:

    go get github.com/filecoin-project/go-jsonrpc
    
  2. Create the following script:

    package main
    
    import (
        "context"
        "fmt"
        "log"
        "net/http"
    
        jsonrpc "github.com/filecoin-project/go-jsonrpc"
        lotusapi "github.com/filecoin-project/lotus/api"
    )
    
    func main() {
        authToken := "<value found in ~/.lotus/token>"
        headers := http.Header{"Authorization": []string{"Bearer " + authToken}}
        addr := "127.0.0.1:1234"
    
        var api lotusapi.FullNodeStruct
        closer, err := jsonrpc.NewMergeClient(context.Background(), "ws://"+addr+"/rpc/v0", "Filecoin", []interface{}{&api.Internal, &api.CommonStruct.Internal}, headers)
        if err != nil {
            log.Fatalf("connecting with lotus failed: %s", err)
        }
        defer closer()
    
           // Now you can call any API you're interested in.
        tipset, err := api.ChainHead(context.Background())
        if err != nil {
            log.Fatalf("calling chain head: %s", err)
        }
        fmt.Printf("Current chain head is: %s", tipset.String())
    }
    
  3. Run go mod init to setup your go.mod file.

  4. You should now to be able to interact with the Lotus API.

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