If you ’re an iPhone user , this scenario probably voice conversant : You direct someone a subject matter , detect that it ’s been delivered and study , and then watch three little dots hover in a conversation bubble as you wait expectantly for a reply . But how does your iPhone know when the person texting you is typing ?
You might have note the telling ellipsis seem only when you ’re sending and receiving via iMessage ; that is , exchanging text with another user on an iPhone , iPad or iPod Touch . In 2011 , Apple introduced iMessage as part of its iOS 5 release [ source : Apple ] . The iMessage service , which is built into the iPhone Messages app , look just like texting but works more like an inst electronic messaging software . When you use your iPhone ’s messaging app to beam a schoolbook to another iMessage user , your phone discern the receiver ’s Apple ID and mechanically sends the message via the iMessage service [ root : Apple ] .
UnlikeSMS text messages , which are sent through your mobile letter carrier ’s cellular internet , iMessage texts are routed through Apple ’s server using a engineering called Apple Push Notification service of process ( APNs ) [ sources : Apple , Dilger , iAnswerGuy ] . The APNs is base on eXtensible Messaging and Presence Protocol ( XMPP ) , the same system used by Google Talk and Apple ’s own iChat instant electronic messaging servicing [ sources : Apple , Dilger ] . XMPP provides a way of life for server to convey with one another , allowing a substance abuser on one host to receive apprisal posted through a unlike host . Whenever you have a connection connection , your iPhone continuously checks with the APNsserversto see whether they have anything new to get off your path , including text subject matter , FaceTime calls or watchful presentment for other apps [ source : Apple , Dilger ] . Because the iPhone at the other close of your schoolbook conversation is also commune with the APNs waiter , the servers are able to observe new activeness , link up it with your Apple ID and get you experience a textbook is on the way .
If your WiFi or cellular net is unavailable , or if you change messages with someone on a unlike mobile operating system , your iPhone will automatically shift from iMessage to standard SMS texting , leaving you in the shadow as to whether anyone has say or start to reply to your message .
