Sending SMS through the Local Server API from Google Apps Script?

[mihvel]

Hello,

I am successfully using the Cloud API of Android SMS Gateway from Google Apps Script. The provided example script (from https://github.com/android-sms-gateway/example-google-apps-script) works fine with the cloud endpoint (https://api.sms-gate.app/3rdparty/v1/messages).

However, I would also like to send SMS messages via the Local Server API (when my phone and computer are on the same LAN). Here is the issue I’m facing:

When I send a request with curl to my phone’s local server (http://192.168.0.21:8080/message), it works correctly. Example:

curl -X POST -u USERNAME:PASSWORD \
  -H "Content-Type: application/json" \
  -d '{"textMessage":{"text":"Test message"},"phoneNumbers":["+38666538695"]}' \
  http://192.168.0.21:8080/message

This sends the SMS without any problem.

But when I try to send the exact same request from Google Apps Script using UrlFetchApp.fetch, the local server always responds with 400 Bad Request. The Cloud API works fine from the same script, so authentication and JSON formatting are correct.

Here is what I have tried in Apps Script (simplified):

const payload = {
  textMessage: { text: "Test message" },
  phoneNumbers: ["+38666538695"]
};

const options = {
  method: "post",
  contentType: "application/json",
  headers: {
    "Authorization": "Basic " + Utilities.base64Encode(username + ":" + password)
  },
  payload: JSON.stringify(payload),
  muteHttpExceptions: true
};

const response = UrlFetchApp.fetch("http://192.168.0.21:8080/message", options);

The request fails with:
Exception: Bad request: http://192.168.0.21:8080/message

So my questions are:

1. Does the Local Server API accept the same JSON+BasicAuth format as the Cloud API, or does it use a different format (e.g., query string parameters like /SendSMS?username=...&password=...&phone=...&message=...)?
2. Is there any known incompatibility between Google Apps Script’s UrlFetchApp and the local server endpoint? (For example, issues with headers, Transfer-Encoding, or Content-Length.)
3. Could you please provide a working Google Apps Script example for sending SMS through the Local Server API (not cloud)?

Thank you very much!

[capcom6]

Hello!

Thank you for using the app.

Here are answers to your specific questions:

1. Yes, the Local Server API uses the same JSON format and Basic Authentication as the Cloud API. The request structure you're using should be identical for both endpoints.

2. There are no known incompatibilities between UrlFetchApp and local server endpoints that would cause 400 Bad Request errors specifically.

3. Your Google Apps Script code appears correct. The problem isn't with the script itself, but with network accessibility.

Google Apps Script runs on Google's servers in their cloud infrastructure, not on your local machine. When your script tries to connect to http://192.168.0.21:8080, it's attempting to reach that IP address from within Google's network, not from your local network. Local IP addresses (like 192.168.x.x) are only accessible from within the same local network.

There are two main options to access the local server outside of your local network:

1. Use a Tunnel Service like ngrok, cloudflared to get a public accessible endpoint.
2. Get a static public IP from your ISP and configure your router to forward external port traffic to your phone's local IP and port.

However, in your case, it is recommended to use a public/private server.

See also https://docs.sms-gate.app/faq/local-server/#why-cant-i-access-the-local-server-from-the-internet

[mihvel]

Yes, that's it! I do not know how I missed it :(
Thank you very much!