Troubleshooting 'received invalid response: 65' Error When Testing a Postgres Connection

Below is what the error could mean and some steps to troubleshoot.

What “received invalid response: 65” May Indicate

This error typically means that while n8n was able to reach the host you provided, the response coming back from the server wasn’t understood as a valid Postgres protocol handshake. In many cases, this can be due to a mismatch between the connection settings on the client (in this case, n8n) and what the server expects.

Possible Causes

• SSL Configuration Mismatch:
  Even though you’ve disabled SSL on your n8n configuration, the Postgres server might be expecting to establish an SSL connection. Double-check your server’s configuration to verify whether it requires SSL.
• Incorrect Host/Port:
  It might be that the IP address or port isn’t connecting directly to a Postgres instance. Some cloud providers may have multiple services listening on the same port or may require additional firewall rules or connection parameters.
• Network Issues or Firewalls:
  If the host has firewalls or IP restrictions (which you mentioned), it’s possible that the connection is reaching an intermediary service or a proxy that isn’t speaking the Postgres protocol.

Troubleshooting Steps

1. Verify SSL Requirements:

   • If the server requires SSL, try enabling SSL in your n8n credentials and select an appropriate SSL mode (e.g., “Require” or “Allow”).
   • If you intended to use a non-SSL connection, ensure the Postgres server is configured to allow non-SSL connections on that port.

2. Double-Check Connection Details:

   • Confirm that the Host (IP address) is indeed the correct server for your Postgres database.
   • Ensure the Port is the Postgres port (default is 5432) and isn’t being intercepted by a different service.

3. Confirm Firewall and Network Settings:

   • Verify that your hosting provider’s IP is authorized and that connections aren’t being redirected or filtered.
   • Check if there’s any proxy or middleware altering the connection response.

4. Test Directly with a Postgres Client:

   • Use a tool like psql (or another Postgres client) from a machine with similar network access to see if you can replicate the issue. For example:

     BASHCopied
     psql -h <your-host> -p <your-port> -U <your-user> -d <your-database>

   • If the connection fails similarly, the issue likely lies with the server configuration or network rather than n8n.

Summary

The error “received invalid response: 65” indicates that the server’s response isn’t matching the expected Postgres protocol response. This can happen when connection details (especially around SSL and host/port settings) do not match what the server requires.

Adjust the settings as suggested above and try testing the connection again.

If further issues persist, consider checking the Postgres server logs for any clues—they may provide more detailed errors that can help pinpoint the mismatch in expected behavior.

The error "received invalid response: 65" indicates that the response from your Postgres server doesn't match what n8n expects from the PostgreSQL protocol during the connection handshake. Essentially, the response code 65 isn’t a valid reply as defined in the protocol. This can happen because of a mismatch between the client’s connection settings and what the server expects.

Below are some potential causes and troubleshooting steps:

Possible Causes

• SSL Configuration Mismatch:
  Even though you have SSL disabled in your n8n settings, your hosting provider’s Postgres server might require SSL. In PostgreSQL’s connection flow, if SSL is expected but a plain connection is initiated (or vice versa), the server could reply with an unexpected byte value (like 65).

• Port or Protocol Mismatch:
  Double-check that you’re using the correct port and that there isn’t any intermediate proxy (or SSH tunnel) altering the handshake.

• Firewall or Network Issues:
  Even if you’ve authorized the IP address, verify that no additional network-level restrictions are interfering with the connection handshake.

Troubleshooting Steps

1. Verify SSL Requirements:
   Confirm with your hosting provider whether SSL encryption is required for connecting to your Postgres instance. If it is, adjust your n8n credentials to enable SSL and, if needed, supply relevant SSL certificates.

2. Double-Check Connection Settings:
   Ensure that the host, port, database, username, and password are correctly set in n8n. Use the suggested queries (like SELECT inet_server_addr(); and SELECT inet_server_port();) on your Postgres server to verify the connection details.

3. Test with Different SSL Modes:
   n8n allows you to choose different SSL modes (Allow, Disable, Require). Try enabling SSL (with the correct mode) to see if that resolves the handshake issue.

By aligning your configuration with the requirements of your hosting provider's Postgres server (especially regarding SSL), you should be able to avoid the invalid response error.