Short answer
Use an HTTP (REST) API to send SMS from applications, OTP flows and multichannel products, because it works with any HTTP library and reports delivery statuses by webhook. Use SMPP v3.4 when you already run an SMPP client or send sustained high volume, since one persistent bind keeps many messages in flight. Many senders use both.
How SMPP and an HTTP API differ
SMPP (Short Message Peer-to-Peer) is a binary telecom protocol that runs over a long-lived TCP session called a bind. An HTTP API sends one HTTPS request per call and returns a response, usually JSON or a message ID.
| Aspect | HTTP API | SMPP v3.4 |
|---|---|---|
| Connection | One HTTPS request per call | One persistent session (bind), ideally over TLS |
| Channels | Often SMS plus WhatsApp, RCS and others | SMS only |
| Delivery receipts | Webhook to your HTTPS endpoint | deliver_sm on the same session |
| Integration effort | Any HTTP library | An SMPP client library and connection management |
| Typical users | Apps, OTP, CRM and e-commerce integrations | Aggregators, resellers and enterprises with SMPP software |
When is SMPP the better choice?
SMPP is asynchronous: a client can send many submit_sm requests before the responses arrive, which is called windowing. That makes it efficient for sustained, high-volume traffic. It also suits companies whose SMS software, gateway or billing system already speaks SMPP.
The cost is operational. You manage reconnects, keep-alive enquire_link messages, receipt acknowledgements and IP allow-listing, and the base protocol has no encryption of its own, so production binds should run over TLS or a VPN.
How to decide
- List the channels you need. If you need WhatsApp, RCS or other channels as well as SMS, start with the HTTP API.
- Check your existing stack. If your platform already has a working SMPP client, SMPP avoids a rewrite.
- Estimate sustained volume and peaks, and ask the provider which interface and throughput it will agree for your account.
- Decide where delivery receipts must land: an HTTPS webhook or your SMPP session.
- Consider running both: HTTP for application and multichannel traffic, SMPP for bulk SMS.
Using both on one account
On OmniChannels.ai, the REST API at https://api.broadnet.me (Bearer token) and SMPP 3.4 over TLS share the same SMS routes, and SMPP binds are provisioned per account by the team rather than self-served.