-1 — EW_BUSY — CNC is busy

The CNC cannot service the request right now and asks you to try again. It does NOT mean the connection failed — that is -16 (EW_SOCKET) or -8 (EW_HANDLE). Treating -1 as a connection failure sends integrators debugging the wrong layer, which is why it is worth stating plainly.

FOCAS is FANUC's own library, not one of Forge's 14 protocol adapters. Forge reaches FANUC controllers over MTConnect, OPC UA, or EtherNet/IP. These codes are documented because anyone integrating a FANUC directly will meet them, and because the fix is often to stop using FOCAS.

Start free All protocols

Diagnosis

When you hit this

Polling faster than the CNC can answer, especially while it is executing a program.
A long-running operation such as a program upload holding the interface.
Several clients issuing requests that serialize inside the controller.

Resolution

How to fix it

Retry after a short delay
EW_BUSY is explicitly retryable. A brief pause and one retry usually succeeds.
Reduce poll frequency
If -1 is constant rather than occasional, the poll loop is simply too fast for the controller.
Do not reconnect on -1
Tearing down and reopening the handle makes it worse and can leak handles into a -16.

Normalization

What Forge does about it

This is a transport failure, so there is nothing for Forge to normalize: the reading never arrives. What Forge does is refuse to let the gap look like good data. The read-time dropout check flags a field that fell to zero and recovered as a communication glitch rather than a real measurement, and the stuck-sensor check fires when a value repeats for 20 consecutive readings — which is what a cached or last-known value looks like after a link drops. Forge does not retry or reconnect for you; that is your client's or your gateway's job.

Connect

Normalize FANUC FOCAS telemetry

One MCP endpoint serves every protocol adapter. 16,908 curated mappings, 366 canonical fields.

# normalize telemetry from FANUC FOCAS — and 13 other protocols

claude mcp add --transport http forge https://mcp.foundrynet.io/mcp \

--header 'Authorization: Bearer YOUR_FORGE_KEY'

✓ forge connected — 32 tools available