How roaming of mobile can be identified

Is there any way to know SIM is in roaming.

Does any AT cmd or any Remote Access Service API provide any h开发者_StackOverflow社区elp over this.

Or any TAPI api on win32 helps me in getting this information?

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The technical definition of "roaming" is that you're not on your home network, i.e. you're talknig to a VLR (Visiting Location Register) instead of a HLR (Home Location Register). Obviously the VLR will be operated by a different company.

[edit] On second thought, you'll see more changes. For instance, you'll also a foreign radio network. I.e. RILCELLTOWERINFO will contain a MCC/MNC that doesn't match your SIM.

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There is a standard AT-command to do this:

AT+CREG?

You have to look at the second value (stat). If it's equal to 5, this means that the device is currently roaming.

For more information please look in the 3GPP TS 27.007 standard.