Ameba Arduino: [RTL8195AM] Let Ameba post articles on Facebook wall

DEPRECATED: Facebook APP posts articles on behalf of users, will no longer be available after Facebook GRAPH API v3.0 (2018/05/01) publication

Facebook is an online social networking website for users to communicate, to share, and to participate in groups. And it provides Graph API for developers to develop applications on different platforms, includes iOS, Android, web application and Facebook Canvas. Applications can make use of users’ resources and services under users’ agreement.

Graph API is based on HTTP protocol API, and this example will use Graph API to let Ameba post articles on the wall of Facebook.

Preparation

• Ameba x 1

Example

• Set up Facebook application

In order to let Ameba access Facebook, we need to set up the application first. The reason is that Facebook needs to know the identity of the users and the applications that require accessing it. Go to the website: https://developers.facebook.com/apps
It will show up the option to be the developers if it is the first time to use it. Then, click to sign up.

Show up a menu and to fill in the job tile and the Facebook agreement policy. Then click Register.

After success, click “Done”

If you have not developed any Facebook application before, it will appear the following menu to choose. We choose “Website” in this example.

Click the “Skip and Create App ID” on the top right

Show up a form and to fill in the following parts:

• Display Name: this name is the one that you will see when you are on the backstage management platform, and it is also the one that shown on Facebook when the application do any activities for users on Facebook. We fill in “ameba” in this example
• Contact Email: it should be filled out already if you have logged in
• Category: according to your application

Then click “Create App ID”

Enter backstage management platform after the instructions. There is an APP ID on the top of the screen, and this ID is used to identify the Facebook application. The APP ID is “312698492463829” in this example. You can set up other options of the application on the backstage management platform, such as OAuth, application domain and the launch process.

• Obtain Access Token

Facebook application will act on behalf of the users on Facebook. That is, it is dangerous to let application to get all the permission. As a result, Facebook application needs an access token. Access token is a long string for Graph API to use in HTTP protocol, and Facebook records every access token and its permissions, its time limits. We can manage our own access token via Graph API Explorer: https://developers.facebook.com/tools/explorer
Here is the brief explanation of the backstage management platform:

• See the menu of the application on the top right, and choose “Graph API Explorer”. We can find out ameba application inside the menu after clicking
• There is a “Get Token” menu under the “Application” menu. You can find out three types of token and we only use “user access token” in this example. Refer to the link about the usage of different access token:
  https://developers.facebook.com/docs/facebook-login/access-tokens
• On the left of “Token Type” is the token value and is represented by string
• The following column are the Graph API commands which the users give. From left to right are:
  • HTTP Request type: according to Graph API manual to fill in the desired HTTP Request type. Usually “GET” or “POST”
  • Graph API Version: Facebook will revise Graph API with different versions. The version is v2.8 in this example. It is allowed to not specify the version when you develop the application and Facebook will use the appropriate oldest version by default
  • Request content: fill in the Graph API parameters. Graph API Explorer will help you to add access token depends upon circumstances
• Debug messages on the center of the screen

Set up the application access token and click “Application”, choose “ameba”

Around the place “Get Token”, click “Get User Access Token”

Then it will show up a menu where you can choose the actions for users of ameba Facebook application. Because we need to post articles on the Facebook wall, we refer to the Graph API document:

https://developers.facebook.com/docs/graph-api/reference/v2.8/group/feed

https://developers.facebook.com/docs/graph-api/reference/v2.8/user/feed

We need the following permission:
publish_actions, user_managed_groups

Then it may show up some warning messages, since Facebook wants to prevent users from being taken advantage of publishing information without the knowledge of the circumstances by the application. As a result, it requests application to provide related policies for users. And we pass this step now in this example unless the application wants to be inspected by Facebook then should we have to make up this part.

And you will be asked if you agree ameba Facebook application to post articles for you or not, then click “OK”.

You will also be asked if you agree ameba Facebook application to manage groups and fan pages for you or not, then click “OK”.

Then go to Graph API Explorer, and the access token gets value now.

We take advantage of Graph API Explorer to test if we now can post articles or not. The fields of HTTP request are filled in as follows:

• HTTP REQ Type: click and choose “POST”
• HTTP REQ content: write “me/feed?message=HelloWorld” and the message part are the contents to be published. The contents are encoded as URI coding

After clicking “Submit” button, the id of the article appears in the debug messages below.

We can take the article id to modify the article, click the Like button and leave comments. The related information of those actions can be found in the Graph API document.

Now we can discover that the ameba Facebook application has already written a post on our Facebook wall. And there is a string “ameba” under the user name of the article.

The operation is to send the HTTP protocol information, and to use openssl to simulate. If you have already installed openssl, please execute:

openssl s_client -connect graph.facebook.com:443

Enter interactive mode, and then input the contents shown below (Do not type wrong words and modify or delete them during this step. These actions will be sent as control characters)。The value which is adjacent to “access_token=” is your access token. And the value for “message=” is HelloWorldV2. Notice to input a space at the end to complete the HTTP command.

POST 
/v2.8/me/feed?access_token=EAAEcZAcqQqtUBAAN0YbAemjZCwvmknqjocENiPwUX92TR7Q54jiKrtyEOR8p2EgfR1RQz3uWeDmEQt9oNYOMaRBqGci55CD9chdXcCQXu1jwXPvLpvPZAMeZBVxWZA94sCEZBVN93ZADDe6XkaJpDxJlvdTF0zATFMZD&message=HelloWorldV2
Host: graph.facebook.com

We should get back the messages below

HTTP/1.1 200 OK
Access-Control-Allow-Origin: *
Pragma: no-cache
Cache-Control: private, no-cache, no-store, must-revalidate
facebook-api-version: v2.8
Expires: Sat, 01 Jan 2000 00:00:00 GMT
Content-Type: text/javascript; charset=UTF-8
x-fb-trace-id: AWAKUnVL1yX
x-fb-rev: 2757773
Vary: Accept-Encoding
X-FB-Debug: 7SqJtuZjt0RZzpAGiknOhcUs0qbDG0Q4WNep592ssnzoc0xRM7IGhsrGy/B38uvGt36vky8rgcfVTD8zuLQ7NA==
Date: Mon, 26 Dec 2016 11:42:36 GMT
Connection: close
Content-Length: 40

{"id":"103964610106403_103999236769607"}closed

One more post on the Facebook wall

You can refer to http url encoder to transfer Chinese to URL values if you need to put space or Chinese in the messageshttp://meyerweb.com/eric/tools/dencoder/
Readers can try this part by your own

• Inspect token and extend token

The access token we got is actually with time limit, and we can use Access Token Debugger to find out the expired time
https://developers.facebook.com/tools/debug/accesstoken/

See the information of the access token, includes the usage by which application, the permission and the expiration (shown by UNIX epoch time). Usually the access token we get from Graph API Explorer is a short-lived token, and it will expire in two hours by default. There is a long-lived access token whose expiration is two months and the time can be extended after the token usage. Click the “Extend Access Token” option on the Access Token Debugger.

New token as below, and the value of long-lived token is different with the value of short-lived token. And we can click the Debug on the bottom right to check the long-lived token value

The expiration time has already extended to two months

Additional notes:

1. According to the Graph API document, Facebook will extend the expiration of the long-lived token to two months at non-regular time if the token is being used. That is, you don’t have to worry about the expiration problem as long as the application makes use of it.
https://developers.facebook.com/docs/facebook-login/access-tokens/expiration-and-extension
However, you have to do the steps to retrieve the new token again if the token isn’t being used until it comes due. And the value of the new token and the old one will not be identical.
2. We can get short-lived token or long-lived token not through the Graph API explorer. Refer to the Graph API document for related details.https://developers.facebook.com/docs/facebook-login/manually-build-a-login-flow

• Post articles on Facebook groups or on fan pages

This part of example is similar with the illustration of writing posts on own Facebook wall. And we just need to get the group id to implement. See the group id on the URL after entering the Facebook group page, the example below is “1210426395661463”.

If the names of the Facebook group or fan page have been modified before, you can use some websites to search for the group id:

http://lookup-id.com/

http://wallflux.com/facebook_id/

Next, we fill in the values below via Graph API Explorer

• HTTP REQ type: “POST”
• HTTP REQ content: “1210426395661463/feed?message=HelloGroup”
  The string of numbers is group id, and the message is modified as HelloGroup

Show up the article id in the Debug information after you click “Submit” button

Go back to the Facebook group page, and you can see that the ameba has already written a post for the user.

Example one：Use Ameba to post articles on Facebook wall

In order to let Ameba write a post on Facebook wall, the steps are similar to the implementation of using openssl to simulate posting. You just need to send HTTP protocol contents via SSL.
We will write a post every minute in this example. However, Facebook will review the post contents to check if it is repeated. Therefore, we change the contents every time we post them with a string array. Open the example on Arduino IDE “File” -> “Examples” -> “AmebaWiFi” -> “Facebook” -> “facebook_feed_publish”

Fill in the information of the desired WiFi AP

Fill in the access token

Set up the target to post. Set as “me” if its own Facebook wall and set as group id if it’s Facebook groups or fan pages

Compile and upload to Ameba to execute, then you can find out that Ameba writes a post for the user

Example one：Code Reference

char server[] = "graph.facebook.com";    // facebook graph api service

char access_token[] = "EAAEcZAcqQqtUBAAN0YbAemjZCwvmknqjocENiPwUX92TR7Q54jiKrtyEOR8p2EgfR1RQz3uWeDmEQt9oNYOMaRBqGci55CD9chdXcCQXu1jwXPvLpvPZAMeZBVxWZA94sCEZBVN93ZADDe6XkaJpDxJlvdTF0zATFMZD";

WiFiSSLClient client;

#define MESSAGE_LIST_SIZE 5
int message_index = 0;
char *message_list[MESSAGE_LIST_SIZE] = {
……

PMS3003 pms(0, 1);

int pm25 = pms.get_pm2p5_air();

PM2.5avg = PM2.5avg * 0.9 + PM2.5now * 0.1