<h4><aclass="anchor"href="#one-user-knows-the-others-number"id="one-user-knows-the-others-number"name="one-user-knows-the-others-number"><iclass="anchor-icon"></i></a>One user knows the other's number</h4>
<p>User A knows phone number of B (for instance, A has B's number in the phone book). But B does not know А's number. User A sends message to B. Immediately prior to sending a message relevant check is executed at the server side and the link between A and B will change automatically: A's number becomes available for B (user A is then presented as constructor <ahref="/constructor/userRequest">userRequest</a>).
The same happens if user B not having A's number sends a message to the latter. A's number also becomes available to B.</p>
<h4><aclass="anchor"href="#users-do-not-know-numbers-of-each-other"id="users-do-not-know-numbers-of-each-other"name="users-do-not-know-numbers-of-each-other"><iclass="anchor-icon"></i></a>Users do not know numbers of each other</h4>
<p>User A has found user B in a chat, geochat or any other way. For both of them phone numbers are not available (in API - constructor <ahref="/constructor/userForeign">userForeign</a>). A starts chat with B. When messaging A's number will not become available for B and vice versa. To provide B with A's number it is necessary to send him personal message with contact info (phone number should be transferred in constructor <ahref="/constructor/inputMediaContact">inputMediaContact</a> using method <ahref="/method/messages.sendMedia">messages.sendMedia</a>).
Now B having personal message with A's phone number can store it in his phone book and import it using method <ahref="/method/contacts.importContacts">contacts.importContacts</a> to have it in contacts. With all that, it is not mandatory for him to send his number: after any message later between them B's number will be available for A (see <ahref="#nomer-odnogo-iz-sobesednikov-izvesten-drugomu">One user knows the other's number</a>).</p>
<h4><aclass="anchor"href="#both-user-know-each-other-number"id="both-user-know-each-other-number"name="both-user-know-each-other-number"><iclass="anchor-icon"></i></a>Both user know each other number</h4>
<p>Since when sending messages to a current user updates on changed links are not sent constructors containing updated links were added to resulting types of messaging methods:</p>
