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How is a client (cellphone) is located by the server in push email. Does it require an active TCP connection to be maintained by the client ? Does the client need to have a public IP for that ?

Achint Mehta
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1 Answers1

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The cellphone must maintain an open connection to the server - almost all cells are behind one or more layers of NAT gateways, making it impossible for the server to reach out to the client unless the client has opened a connection and kept it open.

Marc B
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  • Thanks for the response. So I believe when the client connects to server to check the email in beginning it initiates the TCP session and that is never closed. – Achint Mehta Oct 25 '11 at 02:54
  • It may be different for Blackberries, as those have their own rather unique email push setup. But in general, for your average phone, yes, no mail notices can go server->client until the client has initiated a connection. – Marc B Oct 25 '11 at 02:55