I received an error code, what does it mean?

There are several types of error codes. The following is a list that is not intended to be exhaustive.

Here is a list of status codes in smsmode©, although it is not exhaustive:

0 - Sent.
1 - In progress.
2 - Not sent - Internal error: Sending problem related to a malfunction of the platform.
10 - Expected to be sent.
11 - Received: Confirmed by the operator as received on the recipient's phone.
12 - Partially delivered.
13 - Delivered by the operator: Temporary status, the operator has recognized the recipient's number, but the message has not yet been delivered.
14 - Delivered.
15 - Partially received.
21 - Undeliverable.
22 - Rejected.
31 - Internal error: Sending problem due to a malfunction of the platform.
32 - Authentication error: Check your "username" and "password".
33 - Not sent - insufficient credit: Failed to send due to insufficient credit.
34 - Routing error: Recipient number in an unrecognized format or destination not managed.
35 - Incorrect parameters: "pseudo", "pass", "smsID" are mandatory.
39 - Reception error: Message not delivered for undetermined reason.
36 - Message error.
37 - Message expired.
38 - Message too long: Error in low-cost SMS channel limited to 160 characters.

Temporary Codes:

3501 - Temporary Operator Error: The recipient's number has been recognized by the operator, but the message has not yet been delivered.
3502 - Temporary Absence Error: Message undelivered due to a number that cannot be located by the operator within 24 hours of sending. This number should be considered valid and should not be deleted from the address book.
3503 - Temporary telephone error: Message not delivered due to the terminal (telephone) not being reachable within 24 hours of sending. This number should be considered valid and should not be deleted from the address book.
3504 - Temporary Portability Error.

Permanent Codes:

3521 - Permanent Operator Error: undelivered message due to an unassigned number. This number should be considered invalid and deleted from the address book.
3522 - Permanent Absence Error: Message not delivered due to an unassigned number. This number may be considered incorrect and deleted from the address book.
3523 - Permanent phone error: Message not delivered due to an unassigned number. This number may be considered incorrect and deleted from the address book.
3524 - Permanent anti-spam error.
3525 - Permanent content error.
3526 - Permanent porting error: Number ported to an unknown operator.
3527 - Permanent roaming error.

Other Codes:

3599 - Other error: undefined forwarding problem linked to carrier level malfunction.
3560 - Non-routable number error.
3998 - Invalid message.
3999 - Blacklisted.
50 - Undeliverable.