Configuring a SMPP connection in Morocco: a step-by-step guide for high-volume

The standard solution in the telecom industry is the SMPP (Short Message Peer-to-Peer) protocol.

Although it is extremely fast and asynchronous, setting up a direct SMPP connection with Moroccan gateways requires absolute engineering rigour.

SMPP (currently in v3.4 for most gateways) is a binary protocol running on TCP/IP. Unlike HTTP where you open and close a connection for each sending, SMPP opens a permanent tunnel (a Bind) between your server (ESME) and the provider gateway (SMSC).

What this brings: - Massive Stream: You send a continuous binary stream. No heavy HTTP headers. Throughput is no longer bounded by one HTTP request per message. - Native and asynchronous DLR: Delivery Reports (Delivery Reports) go back from the Moroccan operator (IAM, inwi, Orange) directly into that same TCP tunnel. You no longer need to expose a webhook on your server.

When to use it? The development of a SMPP client takes 10 times more time than an API integration. Use SMPP only if your volume exceeds 1 million SMS per month or if your OTP SLA requires a gateway submission in less than 100 milliseconds.

To establish an SMPP connection with a gateway that offers one (at EnvoiSMS, SMPP is offered only on request, for high volumes; by default, sending goes through our REST API and its bulk endpoint), your provider will provide you with 4 vital elements: IP, Port, System ID (your login) and Password.

But you need to configure your SMPP client behavior optimally:

1. The Bind Type:

Transmitter (TX): Only for sending SMS messages.
Receiver (RX): Only for receiving incoming DLRs and SMS.
Transceiver (TRX): The standard recommendation allows you to send and receive on the same TCP connection.

1. Window Size: This is the secret of the speed of the SMPP. This is the number of messages you can send through the tunnel before waiting for server confirmation (Acknowledge).
2. The Enquiry Link (Keep-alive): Since the tunnel must remain open 24/7, your script must send an enquiry_link every 30 or 60 seconds to prove to the operator server that you are still online.

Never connect directly to the production address. An error loop in your SMPP code can flood the server (unintentional DDoS) and cause your IP to be suspended.

1. Connect to the provider’s SMPP sandbox.
2. Send a submit_sm (the request to send a SMS) with a test number (e.g.: +212600000000).
3. Check the receipt of the submit_sm_resp with a status ESME_ROK (Code 0x00000000), which means that the sending is validated.
4. Leave your client inactive for 10 minutes to check that your 'enquiry_link' mechanismins the connection without Timeout.

• Data Coding Scheme (DCS): This is the #1 problem in Morocco. In SMPP, you must explicitly specify the format of your text. For standard French, use DCS 0x00 (SMSC Default) or 0x01 (ASCII). For the Darija with Arabic characters, you must necessarily convert your text to Hexadecimal and set the DCS to 0x08 (UCS-2).
• The TON/NPI format: For international Moroccan destination numbers (+212), you must configure the TON (Type of Number) to 1 (International) and the NPI (Numbering Plan Indicator) to 1 (ISDN/E.164).
• Queue Drop: If your TCP connection breaks down, any SMS from your RAM not confirmed by the gateway will be lost.Your client must use an external system such as Redis or RabbitMQ to ensure that any non-"Acké" message is back in line for the next reconnection.