Links to phone numbers

There are several URL schemes used by many mobile browsers to communicate with certain mobile phone features.

One of them, the Wireless Telephony Application Interface (WTAI) standard, is part of the WAP 1.X standard (developed in the previous century). WTAI libraries are pre-installed on the phone and other applications (such as the browser) can access them. To use these libraries (if they exist, of course), use the syntax wtai:// /[(;parameter)*].

Call

Remember that most mobile devices are also phones! So why not call a number by clicking on a link? If you are making some kind of business guide or your own unique phone book, then keep in mind that most people prefer to call a specific person rather than fill out a form in the device.

Figure 6.5 demonstrates how link-to-call works on different mobile devices.

Fortunately, there are certain URLs that can help us significantly. The first and almost standard option (copied from Japanese i-Mode standards) involves using the tel scheme:<номер телефона>. This option is called i-Mode mode:

Call us free!

Some devices have the ability to send DTMF tones after the caller has answered. This feature is very useful when calling help desks or voicemails. You can set the link to “call this phone number and after answering, press 2, wait 2 seconds and dial #913.” You can do all this using the postd parameter. The syntax in this case is: ;postd= . You can use numbers, "*" and "#" characters (using a URL encoded value of %23), as well as p to pause for 1 second and w to pause until answered:

Call us free!

Not all mobile devices have this feature, but even if there is no support, it is still possible to call the main phone number. The list of compatible devices for this feature is quite complex and I generally do not recommend relying on it.

When the user activates the call link, a notification is received in response, in which the user is asked to confirm the action (calling the number) and the number is shown in full on the screen (Figure 6.6). This alert is shown to the user to avoid fraud and erroneous calls to premium numbers.

I recommend using the number in the international format: + sign, country code, region (operator) code and the number itself. After all, we don’t know where our user may be, but even if he is in the same country or region as the called subscriber, the international number format will still work.

Rice. 6.6. Nokia and BlackBerry offer call confirmation, and Sony Ericsson's NetFront browser presents the user with a menu offering different ways to interact with this link.

Table 6.8 shows that call link features are not as well supported across platforms as, for example, tel:. There is another way to make a call: using the WTAI standard using the free "wp" library and the "mc" (make call) function:

Call us free!

Also in WTAI, the link can be activated even while making a call, although this feature can only be useful if you are using hands-free mode or a headset. The link includes tones that are sent to the recipient as if the user himself had pressed the required characters on the keyboard, and they are determined using the “sd” (send DTMF tones) function from the “wp” library.

The BlackBerry browser automatically detects phone numbers and email addresses and turns them into links. If you don’t need such a function, you can disable it with a meta tag< http-equiv="x-rim-auto-match" content="none">. Safari has its own meta tag for this case:

iDEN networks (like Nextel) use radio packets to make a call within the network. If your users include subscribers to such networks - for example, they use it for an intranet - then you can provide the user with the ability to make internal calls to other team members (or external calls outside the network) using the Direct Connect URL scheme (dc: ). The Direct Connect URL scheme is compatible with BlackBerry iDEN devices:

Ping John

In some devices, when you click on the tel: link, the user is given the opportunity to select a call option from a menu - voice or video call (this option is only available on 3G networks). In some Japanese phones, a video call via a link must be made using the tel-av protocol:<номер телефона>.

Table 6.8 shows how voice URI schemes work on different platforms.

The iPod Touch is a mobile device, but it's not a phone and doesn't have voice calling capabilities. Instead, the user is prompted to add the number to the phone book using the tel: link.

Sending an email

Some modern devices with browsers also have email applications that are capable of responding to the standard web protocol mailto:. Syntax: mailto: [?parameters]. The parameters detected may vary depending on the device, but typically include "cc", "bcc", "subject", and "body". Parameters are defined in URL format (key=value&key=value) and the values ​​must be URI-encoded.

Here are some examples:

Mail us Mail us Mail us

Keep in mind that the mailto: mechanism does not guarantee that the message will be sent. Typically, it simply opens the email application and the user must confirm sending after making further changes. If you really need to send mail, I recommend using a server-based mechanism.

Typically, if we want to insert a new line into the body of an email message, we use a carriage return plus a line return - characters (%0D%0A). This option does not work correctly with the Mail app on iOS, but we can insert HTML tags into the body, so we can use it in the mobile Safari browser:

Mail us This%20is%20a%20new%20line">Mail us from iPhone

Sending SMS

We all love SMS and that's why mobile browsers usually prompt the user to open a link in a new window directly from the message. To implement this feature, we have two possible URI schemes: sms:// and smsto://. Unfortunately, there is no standard way to know which of these schemes will definitely be compatible with the user's browser.

Later (in Chapter 10) we will look at how to discover the sms: and smsto: compatibility protocol from the server and select the appropriate option.

Syntax: sms://[ ][?parameters]. As you can see, the recipient's number is an option (optional) and therefore you can open the SMS editor from the device without any specific parameters.

Typically the body is specified, but for security reasons this property is not compatible with all mobile devices (for example, to protect the user from sites that send free SMS). As with sending email, SMS is not automatically sent when the user clicks on a link. When clicking on the link, the SMS editor window opens and the user must complete the process manually.

The destination number must either be in international format or, if it is a short number, we must ensure that the user is in the correct country (not roaming) and connected to a service provider compatible with the short number.

BlackBerry enables direct messaging between two BlackBerry devices on the same network. To create a direct message you can use the PIN URL scheme: .

Here are some examples:

Working with MMS

Multimedia Messaging Service (MMS) is a standard way to send a message with multimedia content (images, videos or any other attached content). Symbian devices allow us to use mms URI schemes: to download MMS file from specified URL and mmsto:// to open the multimedia message editor.

Table 6.9 lists support for messaging features across platforms.

To help you develop mobile widgets or offline JavaScript applications, almost every platform has a low-level API for sending and even receiving messages from the application itself. We'll look at these technologies in more detail later (Chapter 12).

Adding a contact to your phone book

It would be nice to offer users to add information about your company (phone number or some other details) to the phone book (contact list). Older WML devices have a WTAI function for this purpose, but newer devices have another, smarter way.

In the WTAI library, "wp" is the function to call, and "ap" (Add to Phonebook) is the function to add to the phone book. The parameters—number and name (optional)—are separated by semicolons. For example:

Add White House to contacts

In the case of modern browsers (those that do not support WTAI, Figure 6.7), the main trick is to create a vCard file (vCard is a standard file format for electronic business cards). If you link to this file, most browsers will send it to the device's Phonebook application and the user will be prompted to add the contact to the phonebook.

Rice. 6.7. We must be careful when using URI schemes on non-compliant devices. The user will not appreciate error messages.

A simple vCard 2.1 file (this version has the best support on mobile devices) will look like this:

BEGIN:VCARD VERSION:2.1 N:Maximiliano;Firtman ORG:O"Reilly Media TITLE:Author TEL;CELL;VOICE:+133MFIRTMAN TEL;WORK;VOICE:+541150320077 END:VCARD

In order for the mobile device to recognize this text file as a valid vCard file, we must send it with the MIME type text/x-vcard. Typically, if the file is static, its extension is .vcf.

For example, we can open the native Facebook iPhone app (if installed) with a list of friends using the URL fb://friends, and if the user has Twitterrific (Twitter client) installed, we can send a message using twitterrific://post? message= . Here's an example:

Tweet this on Twitterrific

When passing URL parameters, be aware of proper encoding of spaces and other characters (for example, use %20 for spaces).

How to detect that an application is installed

What happens if a user clicks on a link in mobile Safari that opens an app, but the app is not installed on their phone? In this case, the browser shows the user a warning and remains on the same page. We can use this technique to improve usability. Make a timer in JavaScript that will start when the user clicks on a link; if the timer countdown ends quickly, it means the user does not have the required application installed and, accordingly, cannot be opened. We can't completely remove the Safari message, but we can send the user an error message indicating that the app is not installed and a link to the App Store where it can be purchased or downloaded.

Local Symbian applications

On Symbian devices we can open applications using the non-standard localapp scheme. For example, to open Calendar, Contacts, or Messages we need to use localapp:calendar, localapp:contacts or localapp:messaging.

Android Intents

Android also has the ability to communicate with other applications using intents. A native Android app can respond to an intent as an explicit call (which is not available for web apps) from a URL or from a MIME type.

For example, to automatically open the installed (and default) PDF viewer on a user's device, the PDF file must be sent with the application/pdf MIME type. To open an application without sending a file, you must use the URI scheme defined by the intent. For example, links to YouTube videos will automatically launch the installed YouTube application (if, of course, the user has set it as the default player).

When the intent is implicit (that is, a URL is used rather than a unique package name), more than one installed application can respond to the URL. In this case, the user receives a window asking him to select the desired application and here he can choose which application will open by default for future use.

On Android, intents can be registered as part of an HTTP URL or can be triggered with a MIME type. For example, if we go to the link http://www.google.com/m/products/scan in the Android browser, it will try to open the Barcode Scanner application.

Internal URLs supported by Android use Google Maps geotags: , ; geo-search for Google Maps: 0.0?q=