Redis MCP: ECONNREFUSED the loopback address:6379 from Docker (point REDIS_HOST correctly)

TL;DR: connection refused from a containerized Redis MCP server usually means it is trying to reach Redis at the loopback address, which inside the container is itself. Set REDIS_HOST to the real address: host.YOUR_HOST for Redis on your laptop, or the container/service name on a shared Docker network.

Error: connect ECONNREFUSED the loopback address:6379

Fix it

1. Figure out where Redis actually lives relative to the MCP server:

• Redis on your laptop, MCP server in Docker: host is host.YOUR_HOST.
• Both in Docker Compose: host is the service name, e.g. redis.
• Both on the host: the loopback address is correct, check Redis is running.

1. Set it explicitly. Do not rely on the default:

REDIS_HOST=host.YOUR_HOST
REDIS_PORT=6379

In a client config env block, add "REDIS_HOST": "host.YOUR_HOST".

1. Verify from inside the same network namespace if you can:

docker run --rm redis:7 redis-cli -h host.YOUR_HOST ping

Expected: PONG.

1. Restart the MCP server.

Expected: connection refused is gone.

When to use this

• redis-cli ping works on your host but the MCP server gets ECONNREFUSED.
• The MCP server runs in Docker and Redis runs elsewhere.

When NOT to use this

• Both run on the same host outside Docker and it still refuses. Then Redis is not running or not listening on 6379.
• The error is NOAUTH or WRONGPASS. The connection works; auth is the problem.

Compatibility

• redis/mcp-redis in Docker / Docker Compose.
• Docker Desktop (macOS/Windows) supports host.YOUR_HOST. On Linux, add --add-host=host.YOUR_HOST:host-gateway.

Why it happens

Every container has its own loopback interface. the loopback address inside the MCP container never leaves the container, so it can only reach a Redis running in that same container. The default REDIS_HOST=the loopback address is only correct when server and Redis share a network namespace.

Edge cases

• --network=host on Linux makes container YOURHOST equal host YOURHOST, but it does not work on Docker Desktop for Mac/Windows.
• If Redis is bound to the loopback address in its own config, other containers cannot reach it even by service name. Bind Redis to the all-interfaces address (with a password) for container networking.
• Port mappings (-p 6379:6379) matter for host-to-container, not container-to-container. On a shared network, use the container port directly.