Two-way SMS API using your own number
SimGate handles both directions: send texts via API and receive replies as signed webhooks. Set up keyword auto-replies and automation rules — all from your own SIM.
Both directions over one API
Most SMS APIs are outbound-only, or treat inbound as a paid add-on. SimGate handles both directions from day one: send texts via the REST API and receive replies as signed webhook events — no separate product to enable.
Because both the outbound sends and the inbound webhook come from the same SIM, the conversation thread looks natural to your users. They reply to the same number that texted them, and the reply lands in your backend within seconds.
Automation rules let you configure keyword-based responses without any code — useful for confirming appointments, routing support requests, or running simple opt-out flows.
How two-way SMS works with SimGate
Send the first message
POST to /v1/sms/send with your API key, device ID, phone number, and message body. The text goes out through your connected SIM.
User replies to your number
The reply arrives on the same SIM. SimGate captures it and triggers your inbound webhook within seconds.
Your backend receives the webhook
A signed POST lands on your webhook URL with the sender number, message body, device ID, and timestamp. Verify the signature and process the reply.
Send a follow-up (optional)
Use the sender number from the webhook payload to POST another outbound message, continuing the conversation thread.
Inbound webhook payload
1{2"id": "evt_123",3"type": "sms.received",4"createdAt": "2026-06-24T12:34:56.000Z",5"data": {6"deviceId": "android-5q15b182f2704gbz",7"from": "+1234567890",8"body": "YES",9"receivedAt": "2026-06-24T12:34:55.000Z"10}11}
Every inbound SMS to your SIM triggers a POST to your webhook URL with this payload.
What you can build
- Appointment confirmation flows (send reminder → user replies YES/NO → auto-confirm)
- Support ticket intake via SMS — reply to open a ticket
- Opt-out handling — keyword STOP removes the number from your list
- Two-way verification — send a code, receive the reply, confirm in one round trip
- Simple conversational bots triggered by incoming keywords
Automation rules without code
The SimGate dashboard lets you configure keyword-based automation rules — e.g. reply 'CONFIRMED' when the sender includes 'YES', or forward specific senders to a second webhook. For simple flows you don't need to write any webhook-handling code.
Frequently asked questions
How do I receive inbound SMS with SimGate?
Configure your inbound webhook URL in the SimGate dashboard. Every SMS that arrives on your connected SIM will trigger a signed POST to that URL with the sender number, message, and metadata.
How do I verify the webhook is genuinely from SimGate?
Set a webhook secret in the dashboard. SimGate signs every inbound event with that secret and includes the signature in the request headers so you can verify it before processing.
Can I auto-reply without writing backend code?
Yes — create an automation rule in the dashboard. Rules match on sender number, message content, or keywords and send a configurable reply through your SIM automatically.
Is inbound SMS included in the plan price?
Yes. Inbound SMS delivery via webhooks is included in every SimGate plan at no extra charge.
What happens if my webhook endpoint is temporarily down?
SimGate retries failed webhook deliveries automatically. You can see delivery attempts and errors in the dashboard.
Keep exploring
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