docs: Tutorial: transfer-files (previsously #714) (#774)

examples/transfer-files/.gitignore

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+public/js/ipfs.js

examples/transfer-files/README.md

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+# Tutorial - Transfer files between the browser and other IPFS nodes
+
+> Welcome! This tutorial will help you exchange files between browser nodes and go-ipfs nodes.
+
+There are a couple of caveats:
+
+- js-ipfs currently doesn't support DHT peer discovery, the peer from which you are fetching data should be within the reach (local or in public IP) of the browser node.
+- We need to use a signalling server to establish the WebRTC connections, this won't be necessary as soon as libp2p-relay gets developed
+
+That being said, we will explain throughout this tutorial to circunvent the caveats and once they are fixed, we will update the tutorial as well.
+
+## Application diagram
+
+The goal of this tutorial is to create a application with a IPFS node that dials to other instances of it using WebRTC, and at the same time dial and transfer files from a Desktop IPFS node using WebSockets as the transport.
+
+```
+┌──────────────┐                   ┌──────────────┐
+│   Browser    │                   │   Browser    │
+│              │      WebRTC       │              │
+│              │◀─────────────────▶│              │
+└──────────────┘                   └──────────────┘
+        ▲                                  ▲
+        │                                  │
+        │WebSockets              WebSockets│
+        │        ┌──────────────┐          │
+        │        │   Desktop    │          │
+        └───────▶│              │◀─────────┘
+                 └──────────────┘
+```
+
+## Check out the final state
+
+In the end, you should get an app running, something like this:
+
+![](https://ipfs.io/ipfs/Qmbti2nBZWxQLhpggB7tC3HvcxTMivmMo3MVwQveAsHBAE)
+
+## Step-by-step instructions
+
+Here's what we are going to be doing, today:
+
+- 1. Set up, install a go-ipfs node in your machine
+- 2. Make your daemons listen on WebSockets
+- 3. Start the WebApp
+- 4. Dial to a node using WebSockets (your Desktop ones)
+- 5. Transfer files between all of your nodes, have fun!
+
+Let's go.
+
+### 1. Set up
+
+You'll need to have an implementation of IPFS running on your machine. Currently, this means either go-ipfs or js-ipfs.
+
+Installing go-ipfs can be done by installing the binary [here](https://ipfs.io/ipns/dist.ipfs.io/#go-ipfs). Alternatively, you could follow the instructions in the README at [ipfs/go-ipfs](https://github.com/ipfs/go-ipfs).
+
+Installing js-ipfs requires you to have node and [npm](https://www.npmjs.com). Then, you simply run:
+
+```sh
+> npm install --global ipfs
+...
+> jsipfs --help
+Commands:
+...
+```
+
+This will alias `jsipfs` on your machine; this is to avoid issues with `go-ipfs` being called `ipfs`.
+
+At this point, you have either js-ipfs or go-ipfs running. Now, initialize it:
+
+```sh
+> ipfs init
+# or
+> jsipfs init
+```
+
+This will set up your IPFS repo in your home directory.
+
+### 2. Make your daemons listen on WebSockets
+
+At this point, you need to edit your `config` file, the one you just set up with `{js}ipfs init`. It should be in either `~/.jsipfs/config` or `~/.ipfs/config`, depending on whether you're using JS or Go.
+
+Note: js-ipfs sets up a websocket listener by default, if you are just using js-ipfs you can skip this test.
+
+Since websockets support is currently not on by default, you'll need to add a WebSockets address manually. Look into your config file and find the `Addresses` section:
+
+```json
+  "Addresses": {
+    "Swarm": [
+      "/ip4/0.0.0.0/tcp/4002"
+    ],
+    "API": "/ip4/127.0.0.1/tcp/5002",
+    "Gateway": "/ip4/127.0.0.1/tcp/9090"
+  }
+```
+
+Add the following entry to your `Swarm` array: `/ip4/127.0.0.1/tcp/9999/ws`. Now, it should look like this: 
+
+```json
+  "Addresses": {
+    "Swarm": [
+      "/ip4/0.0.0.0/tcp/4002",
+      "/ip4/127.0.0.1/tcp/9999/ws"
+    ],
+    "API": "/ip4/127.0.0.1/tcp/5002",
+    "Gateway": "/ip4/127.0.0.1/tcp/9090"
+  }
+```
+
+Now it should listen on Websockets. We're ready to start the daemon.
+
+```sh
+> ipfs daemon
+```
+
+(Again, either `jsipfs` or `ipfs` works. I'll stop repeting this from here on out.)
+
+You should see the Websocket address in the output:
+
+```sh
+Initializing daemon...
+Swarm listening on /ip4/127.0.0.1/tcp/4001
+Swarm listening on /ip4/127.0.0.1/tcp/9999/ws
+Swarm listening on /ip4/192.168.10.38/tcp/4001
+Swarm listening on /ip4/192.168.10.38/tcp/9999/ws
+API server listening on /ip4/127.0.0.1/tcp/5001
+Gateway (readonly) server listening on /ip4/0.0.0.0/tcp/8080
+Daemon is ready
+```
+
+It's there in line 5 - see the `/ws`? Good. that means it is listening.
+
+### 3. Start the WebApp project
+
+Now, you'll need to make sure you are in `js-ipfs/examples/transfer-files`. You'll see a `package.json`: this manifest holds the information for which packages you'll need to install to run the webapp. Let's install them, and then start the project:
+
+```sh
+> npm install
+> npm start
+```
+
+You should see this text:
+
+```sh
+Starting up http-server, serving public
+Available on:
+  http://127.0.0.1:12345
+  http://192.168.1.24:12345
+Hit CTRL-C to stop the server
+```
+
+Go to http://127.0.0.1:12345 in your browser; you're now in the webapp, if all went well.
+
+### 4. Dial to a node using WebSockets (your Desktop ones)
+
+On your terminal, run `ipfs id` to find the WebSockets address that it is listening on. Should look like this: `"/ip4/127.0.0.1/tcp/4003/ws/ipfs/<your peer id>". Important, your node must be running in order to have listeners, to do so, run in another tab of your terminal: `ipfs daemon`.
+
+![](https://ipfs.io/ipfs/Qme9RM3SSyb57PGA7n5bEhwhMwS8fDrMZ8zzKkrwncRcfm)
+![](https://ipfs.io/ipfs/QmdFX4wJkKpryisjGQGt88Yr8zaQM9zMPL3xzK2YGTUMNM)
+
+### 5. Transfer files between all of your nodes, have fun!
+
+Now you can drag an drop files on the browser or add them through the CLI with `ipfs add <file>` and with the fetch file box, you can retrieve the file to the browser or other browser tabs!
+
+![](https://ipfs.io/ipfs/QmcVNbhmMFzz9x2mY33GPGetibFGXXD7dYd3kDa7eKEUyw)
+![](https://ipfs.io/ipfs/QmZcRvGQtM7mnSWKqFwptCYoBitBJaGBKLLjvzENfzXFMi)

examples/transfer-files/img/diagram.txt

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+┌──────────────┐                   ┌──────────────┐
+│   Browser    │                   │   Browser    │
+│              │      WebRTC       │              │
+│              │◀─────────────────▶│              │
+│              │                   │              │
+└──────────────┘                   └──────────────┘
+        ▲                                  ▲
+        │                                  │
+        │                                  │
+        │                                  │
+        │WebSockets              WebSockets│
+        │                                  │
+        │                                  │
+        │        ┌──────────────┐          │
+        │        │   Desktop    │          │
+        │        │              │          │
+        └───────▶│              │◀─────────┘
+                 │              │
+                 └──────────────┘

examples/transfer-files/package.json

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+{
+  "name": "transfer-files",
+  "version": "1.0.0",
+  "scripts": {
+    "check-bundle": "test -f ../../dist/index.js && npm run copy-bundle || (echo \"js-ipfs dist file not found, go up two dirs and run 'npm run build' first\" && exit 1)",
+    "copy-bundle": "cp ../../dist/index.js ./public/js/ipfs.js",
+    "serve": "http-server -c-1 -p 12345 public",
+    "start": "npm run check-bundle && npm run serve"
+  },
+  "license": "MIT",
+  "devDependencies": {
+    "http-server": "^0.9.0"
+  }
+}