SMS Gateway for Android™: A Simple and Private SMS Gateway for Your Projects

In the world of digital communications, SMS remains a vital channel for authentication, notifications, and instant alerts. SMS Gateway is a solution that allows you to quickly and easily integrate SMS functionality into your projects by using an Android smartphone as a gateway.

It was created by a developer, for developers, with a focus on ease of use, data privacy, and the principles of open-source software. There’s no UI—just an API. What else could a developer need?

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From Idea to Implementation

SMS Gateway started as a personal project but quickly found demand among other users. Today, its primary goals are simplicity and privacy. These goals are achieved while keeping costs minimal and ensuring the product remains completely free and open source.

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Three Modes of Operation

The app operates in three modes, all sharing the same API:

1. Local
   
   REST API runs directly on the Android device, enabling operation without the need for an external server. This mode allows entirely offline operation within a local network, ensuring enhanced privacy without requiring internet access.

2. Cloud
   
   If direct access to the device is not possible, requests are routed through a shared server. This mode is free to use unless message volumes impact other users. For enhanced privacy, end-to-end encryption is available.

3. Private
   
   For maximum security, you can deploy your own server instance. In this mode, your messages never leave your infrastructure. While push notifications still rely on the Cloud server, no message content is ever shared.

And because the app is open source, you can even build your own version of the service to suit your specific needs.

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Webhooks for Incoming Messages

SMS Gateway can be used not only to send messages but also to receive incoming SMS messages directly to your backend. Webhooks make it easy to process incoming messages in real time without storing them on third-party servers.

How It Works

When an SMS is received, the app sends a POST request to the configured webhook URL. The payload includes details like:

• Sender’s phone number
• Message content
• Timestamp

Developers can use this to process responses, trigger automated workflows, or store the data securely.

Learn more in the webhook documentation.

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Why Choose SMS Gateway?

Here are several key advantages that make SMS Gateway stand out among competitors:

• No Registration: You don’t need to provide an email or phone number to start using the application.
• Privacy:
  • Supports end-to-end encryption, private servers, and webhooks sent directly from the device for maximum privacy.
  • All message data on the Cloud server is hashed within 15 minutes after the app acknowledges receipt of the queued message.
• Simple Setup:
  • Start with the Cloud server—all you need is an Android device running the app.
  • Deploy a Private server with a single command using Docker if you need more privacy.
• Webhooks Support: Real-time delivery of incoming SMS directly to your system with privacy-first features.
• Multiple SIMs Support: Use devices with multiple SIM cards to manage different numbers easily. You can specify SIM usage explicitly or enable the SIM rotation feature.
• Developer Tools:
  • A CLI utility for sending SMS directly from the command line.
  • Libraries for popular programming languages: Go, Python, JavaScript/TypeScript, PHP.

And all of this is completely free.

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Technical Stack

SMS Gateway is built using:

• Go for the backend
• Kotlin for the Android app
• MariaDB for data storage
• Docker Swarm for orchestration
• Terraform for infrastructure automation

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Usage Examples

REST API Example

Send an SMS using the local REST API:

curl -X POST -u <username>:<password> \
  -H "Content-Type: application/json" \
  -d '{ "message": "Hello, doctors!", "phoneNumbers": ["+19162255887", "+19162255888"] }' \
  https://api.sms-gate.app/3rdparty/v1/message
</password></username>

Replace and with the credentials available on the Home tab of the Android app.

CLI Utility Example

Send SMS using the CLI utility:

# Send a message
smsgate send --phone '+19162255887' 'Hello, Dr. Turk!'

# Send a message to multiple numbers
smsgate send --phone '+19162255887' --phone '+19162255888' 'Hello, doctors!'
# or
smsgate send --phones '+19162255887,+19162255888' 'Hello, doctors!'

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Who Is This For?

SMS Gateway is ideal for:

• Small and medium businesses needing quick and affordable SMS integration.
• Developers seeking a flexible, secure, and open-source solution.
• Privacy enthusiasts who want to avoid relying on third-party cloud services.

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Limitations

The app is not for you if your goal is to send large batches of messages, such as for advertisements or spam campaigns. Although it includes features to mitigate mobile operator restrictions, SMS Gateway is designed for legitimate, low-volume use cases. For bulk messaging, consider specialized services.

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Conclusion

SMS Gateway prioritizes user privacy and convenience. With no registration required, flexible configuration options, and completely free access, it’s a reliable solution for any SMS-related tasks.

With its seamless setup, focus on privacy, robust webhook support, and open-source principles, SMS Gateway is the ultimate tool for integrating SMS functionality into your applications.

Ready to try it out? Start now: SMS Gateway or contact me via comments.

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