SIM808 2G GSM模块基于SSL连接Google Cloud/Firebase的技术咨询

Got it, let's break down your problem first. The HTTP 606 error from your SIM808 is almost certainly due to an SSL protocol mismatch—Google Cloud (including Firebase) has long deprecated older SSL versions like SSLv3, and since your module only supports SSL (not TLS), it can't complete the handshake with Firebase's endpoints directly. Here's how you can resolve this, with both direct (if feasible) and indirect approaches:

Before jumping to workarounds, let's rule out quick fixes:

• Update SIM808 firmware: Some older firmware builds might have limited SSL support, but a newer version could add basic TLS 1.0/1.1 compatibility (note: Google Cloud now blocks TLS 1.0, so this is a long shot, but worth checking SIMCom's official firmware channels).
• Force maximum supported SSL version: Use AT commands to set the highest SSL version your module can handle. For example:
  • Enable SSL for HTTP: AT+HTTPSSL=1
  • Set SSL version to SSLv3 (check your module's AT manual for valid values): AT+SSLCFG="VERSION",1
• Caveat: Even if you force SSLv3, Google Cloud's endpoints will almost certainly reject the connection, as they no longer support this outdated protocol. This approach is mostly for troubleshooting.

Since direct connection isn't feasible, you'll need a proxy server to act as a bridge: it accepts SSL connections from your SIM808 (using the SSL version it supports) and forwards requests to Firebase using modern TLS protocols that Google Cloud accepts.

Step 1: Set Up the Proxy Server #

You can use a lightweight server like Node.js or Nginx. Here's a simple Node.js example:

const https = require('https');
const fs = require('fs');

// SSL certificate for the proxy (generate self-signed or use Let's Encrypt for production)
const proxySSLConfig = {
  key: fs.readFileSync('proxy-private-key.pem'),
  cert: fs.readFileSync('proxy-public-cert.pem')
};

// Create HTTPS server to listen for SIM808 requests
https.createServer(proxySSLConfig, (simRequest, proxyResponse) => {
  // Forward request to Firebase Realtime Database
  const firebaseRequest = https.request({
    hostname: 'your-firebase-project-id.firebaseio.com',
    path: simRequest.url,
    method: simRequest.method,
    headers: simRequest.headers
  }, (firebaseResponse) => {
    proxyResponse.writeHead(firebaseResponse.statusCode, firebaseResponse.headers);
    firebaseResponse.pipe(proxyResponse);
  });

  simRequest.pipe(firebaseRequest);
}).listen(443, '0.0.0.0');

• Generate a self-signed SSL certificate for testing with OpenSSL: openssl req -x509 -newkey rsa:4096 -keyout proxy-private-key.pem -out proxy-public-cert.pem -days 365
• Host this server on a cloud instance (like Google Cloud Compute Engine) or a local machine with a public IP address.

Step 2: Configure SIM808 to Use the Proxy #

• Import proxy certificate: If your SIM808 supports certificate storage, import the proxy's public certificate using an AT command like AT+SSLCFG="CACERT",1,"proxy-public-cert.pem" (verify exact syntax in your module's manual).
• Disable certificate validation (testing only): For quick testing, turn off certificate checks with AT+SSLCFG="CV",0 (never do this in production).
• Target the proxy in requests: Replace Firebase's URL with your proxy server's address. For example, to fetch data from a users node, use AT+HTTPPARA="URL","https://your-proxy-server.com/users.json"
• Send requests as usual: Enable SSL with AT+HTTPSSL=1, then use AT+HTTPACTION=0 (GET) or AT+HTTPACTION=1 (POST) to execute the request.

Alternative: MQTT Bridge #

If your use case works with MQTT instead of HTTPS:

• SIM808 supports MQTT over SSL. Set up an MQTT broker (like Mosquitto) that acts as a bridge to Firebase.
• The broker accepts MQTT connections from your SIM808 via SSL, then forwards messages to Firebase Realtime Database using its REST API or official SDK.

• Always use valid, trusted SSL certificates (not self-signed) for your proxy in production.
• Secure your proxy with firewall rules to only allow connections from your SIM808's IP address.
• Test the proxy first with tools like curl to confirm it forwards requests correctly: curl https://your-proxy-server.com/users.json

内容的提问来源于stack exchange，提问作者narayan rathod