Milvus MCP: connection refused (http/https and port mismatch in MILVUS_URI)

TL;DR: Connection refused with Milvus is usually the wrong scheme or port in MILVUS_URI. Local Docker Milvus is the service URL for that host and port. Zilliz Cloud is https://. Match the URI to the deployment.

Connection refused (Milvus)

(With MILVUS_URI set to a mismatched scheme or port.)

Fix it

1. Identify your deployment:

• Local Docker: the service URL for that host and port (plaintext, port 19530).
• Zilliz Cloud: the service URL for that host and port or the exact endpoint from the dashboard.

1. Set it correctly:

{
  "env": {
    "MILVUS_URI": "http://YOUR_MILVUS_HOST:19530"
  }
}

1. Restart the MCP client and validate with the list-collections tool.

Expected: connection succeeds.

When to use this

• Connection refused and the URI mixes https:// with port 19530, or http:// with a cloud endpoint.
• It worked locally and broke when pointed at Cloud (or vice versa).

When NOT to use this

• Permission denied with a good connection. That is the token, not the URI.
• Timeout with the right URI. Firewall or routing.

Compatibility

• zilliztech/mcp-server-milvus.
• Self-hosted Milvus, Zilliz Cloud.

Why it happens

Milvus serves plaintext gRPC on 19530 and TLS on the cloud endpoints. The scheme and port are a pair; mixing them points the client at a listener that speaks the other protocol, and the handshake dies as connection refused rather than a helpful message.

Edge cases

• Some self-hosted setups enable TLS on 19530. Then use https:// with that port and the right CA.
• Copy the cloud endpoint verbatim from the dashboard. Guessing the hostname pattern fails when regions differ.
• Docker: from inside a container, YOUR_HOST is the container. Use host.YOUR_HOST or the service name.