Error Handling

Common error codes & handling.

In SMPP, each response PDU contains a command_status field that indicates whether a request was successful or if an error occurred. Error codes are numeric values that help identify the cause of failure. Proper handling of these errors helps maintain the connection and ensures the delivery of messages. Below are some common error codes for reference, but the full list is much more extensive:

• ESME_ROK (0x00000000): No Error – The operation was successful.
  • Proceed with the next operation.
• ESME_RINVMSGLEN (0x00000001): Invalid Message Length – The PDU length is incorrect.
  • Recalculate the length and resend the PDU.
• ESME_RINVCMDID (0x00000003): Invalid Command ID – The command is unsupported or incorrectly specified.
  • Verify the command ID and resend if corrected.
• ESME_RINVBNDSTS (0x00000004): Invalid Bind Status – The request is incompatible with the current session state.
  • Rebind with the correct mode (TX, RX, or TRX).
• ESME_RSYSERR (0x00000008): System Error – An internal SMSC error occurred.
  • Retry after a short delay or escalate to the SMSC administrator.
• ESME_RTHROTTLED (0x00000058): Throttling Error – The rate of PDU submission exceeds the allowed limit.
  • Reduce the sending rate and retry after a delay.

Retries and failover mechanisms.

Retries and failover mechanisms are used to ensure message delivery even if temporary failures occur. SMPP supports several strategies for handling retries and failover:

• Automated Retries for Temporary Errors: For errors like ESME_RTHROTTLED (throttling) or ESME_RSYSERR (system error), implement automated retry mechanisms with progressive backoff (e.g., retry after 5s, 10s, 30s). Limit the maximum retry count to prevent endless loops.
• Store and Forward: If a message cannot be delivered immediately, the SMSC may store it temporarily and retry delivery based on the validity period. Ensures that messages reach their destination even if the recipient is temporarily unavailable.
• Alternative Routes (Failover): Use multiple SMSC connections or SMPP gateways as backup routes if the primary SMSC is unreachable. Implement load balancing to distribute traffic evenly across multiple connections.
• Message Expiry: Define a validity period for each message to prevent retrying indefinitely. If a message expires before being delivered, the SMSC returns a delivery receipt with a status of “EXPIRED”.