Uploading Files to Swarm

In the previous section we setup a swarm node running as a daemon on port 8500. Now import the swarm package go-ethereum swarm/api/client. I'll be aliasing the package to bzzclient.

import (
  bzzclient "github.com/ethereum/go-ethereum/swarm/api/client"
)

Invoke NewClient function passing it the swarm daemon url.

client := bzzclient.NewClient("http://127.0.0.1:8500")

Create an example text file hello.txt with the content hello world. We'll be uploading this to swarm.

hello world

In our Go application we'll open the file we just created using Open from the client package. This function will return a File type which represents a file in a swarm manifest and is used for uploading and downloading content to and from swarm.

file, err := bzzclient.Open("hello.txt")
if err != nil {
  log.Fatal(err)
}

Now we can invoke the Upload function from our client instance giving it the file object. The second argument is an optional existing manifest string to add the file to, otherwise it'll create on for us. The third argument is if we want our data to be encrypted.

The hash returned is the swarm hash of a manifest that contains the hello.txt file as its only entry. So by default both the primary content and the manifest is uploaded. The manifest makes sure you could retrieve the file with the correct mime type.

manifestHash, err := client.Upload(file, "", false)
if err != nil {
  log.Fatal(err)
}

fmt.Println(manifestHash) // 2e0849490b62e706a5f1cb8e7219db7b01677f2a859bac4b5f522afd2a5f02c0

Now we can access our file at bzz://2e0849490b62e706a5f1cb8e7219db7b01677f2a859bac4b5f522afd2a5f02c0 which learn how to do in the next section.

Full code

Commands

geth account new
export BZZKEY=970ef9790b54425bea2c02e25cab01e48cf92573
swarm --bzzaccount $BZZKEY

hello.txt

hello world

swarm_upload.go

package main

import (
    "fmt"
    "log"

    bzzclient "github.com/ethereum/go-ethereum/swarm/api/client"
)

func main() {
    client := bzzclient.NewClient("http://127.0.0.1:8500")

    file, err := bzzclient.Open("hello.txt")
    if err != nil {
        log.Fatal(err)
    }

    manifestHash, err := client.Upload(file, "", false)
    if err != nil {
        log.Fatal(err)
    }
    fmt.Println(manifestHash) // 2e0849490b62e706a5f1cb8e7219db7b01677f2a859bac4b5f522afd2a5f02c0
}