What is SMPP?
SMPP (Short Message Peer-to-Peer) is an open, industry-standard protocol used to exchange SMS messages between SMS service centres (SMSCs) and external applications (ESMEs — External Short Message Entities). It's the protocol of choice for high-throughput, enterprise-grade SMS sending.
BulkSMSRates supports SMPP v3.4 with TLS encryption on port 2775 (plain) and port 2776 (TLS). Our gateway supports transmitter, receiver, and transceiver bind modes.
SMPP Architecture
In an SMPP setup, your application (ESME) connects to our SMPP gateway (SMSC) over TCP/IP. The connection is persistent — unlike HTTP, you maintain an open socket and can send messages at high throughput without connection overhead.
Key components:
• ESME (External Short Message Entity): Your application
• SMSC (Short Message Service Centre): BulkSMSRates gateway
• PDU (Protocol Data Unit): The binary message format
• Bind: Authentication handshake to establish a session
• TPS (Transactions Per Second): Throughput rate per bind
Connection Details
Use the following parameters to connect to the BulkSMSRates SMPP gateway:
| Parameter | Value |
|---|---|
| Host | smpp.bulksmsrates.com |
| Port (plain) | 2775 |
| Port (TLS) | 2776 |
| SMPP Version | 3.4 |
| System ID | Your API username |
| Password | Your SMPP password |
| System Type | Leave empty or use "SMPP" |
| Max TPS | 100 (upgradeable) |
| Max Binds | 5 per account |
Bind Types
SMPP supports three bind types:
• bind_transmitter: Send-only mode. Used if you only need to submit messages.
• bind_receiver: Receive-only mode. Used to receive DLR (delivery reports) and MO (mobile-originated) messages.
• bind_transceiver: Send and receive. Recommended — single connection for both outbound and inbound traffic.
For most integrations, use bind_transceiver to handle outbound SMS and incoming DLRs on the same session.
// Example bind_transceiver PDU (hex)
00 00 00 27 // command_length: 39
00 00 00 09 // command_id: bind_transceiver
00 00 00 00 // command_status: 0 (OK)
00 00 00 01 // sequence_number: 1
// Body:
"myusername " // system_id (null-terminated)
"mypassword " // password (null-terminated)
"SMPP " // system_type
34 // interface_version: 0x34 = v3.4
00 // addr_ton
00 // addr_npi
" " // address_rangeKey PDU Types
SMPP communication uses Protocol Data Units (PDUs) — binary packets with a fixed header and variable body.
| PDU | Direction | Purpose |
|---|---|---|
| bind_transceiver | ESME→SMSC | Authenticate and open session |
| bind_transceiver_resp | SMSC→ESME | Authentication response |
| submit_sm | ESME→SMSC | Submit a message for delivery |
| submit_sm_resp | SMSC→ESME | Acknowledge message submission |
| deliver_sm | SMSC→ESME | Inbound MO or DLR callback |
| deliver_sm_resp | ESME→SMSC | Acknowledge delivery receipt |
| enquire_link | Either | Keepalive (every 30–60s) |
| enquire_link_resp | Either | Keepalive response |
| unbind | Either | Gracefully close session |
Sending a Message (submit_sm)
To send an SMS via SMPP, construct a submit_sm PDU. Key fields:
submit_sm fields:
- service_type: "" (empty)
- source_addr_ton: 5 (alphanumeric) or 1 (international)
- source_addr_npi: 0
- source_addr: "YourBrand" or "+447700900001"
- dest_addr_ton: 1 (international)
- dest_addr_npi: 1
- destination_addr: "447700900000" (no + prefix)
- esm_class: 0 (default, no UDH)
64 (0x40, UDH present for multipart)
- data_coding: 0 (GSM-7)
8 (UCS-2)
- registered_delivery: 1 (request DLR)
- short_message: "Hello World" (up to 254 bytes)Receiving Delivery Reports (DLR)
When registered_delivery=1, you receive a deliver_sm PDU from the SMSC containing the delivery status. Parse the short_message body to extract the DLR:
DLR format: id:MSGID sub:001 dlvrd:001 submit date:YYMMDDHHMM done date:YYMMDDHHMM stat:DELIVRD err:000 text:FIRST20CHARS
Stat values: DELIVRD (delivered), UNDELIV (undelivered), EXPIRED, DELETED, UNKNOWN, REJECTED.
See our DLR Codes guide for a complete list of error codes.
Best Practices
1. Use enquire_link keepalives every 30–60 seconds to prevent connection timeouts.
2. Implement reconnection logic with exponential backoff (retry after 1s, 2s, 4s, 8s, etc.).
3. Process incoming PDUs asynchronously — don't block the read loop on business logic.
4. Use window size appropriately — submit up to 10 messages without waiting for responses (async).
5. Handle submit_sm_resp errors — check command_status and log failures.
6. Use TLS (port 2776) in production to protect message content in transit.
7. Test with our sandbox endpoint before going live: smpp-sandbox.bulksmsrates.com:2775.
Related Guides
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