-16 — EW_SOCKET — socket communication error

The Ethernet layer failed: the socket could not be opened, or an established socket broke. This is the code most integrators mean when they say FOCAS will not connect.

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.

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Diagnosis

When you hit this

Wrong IP or port. FOCAS listens on 8193 by default, which is frequently blocked or remapped.
The controller's connection slot limit is reached. Many FANUC controllers allow only a handful of concurrent FOCAS clients, and an abandoned handle occupies one until it times out.
cnc_allclibhndl3 called without a matching cnc_freelibhndl, leaking handles until the CNC refuses new connections.

Resolution

How to fix it

Free every handle
Each cnc_allclibhndl3 must be paired with cnc_freelibhndl, including on error paths. Leaked handles are the most common cause of -16 appearing after hours of successful operation.
Respect the connection limit
Count how many clients touch the controller. A second SCADA system or a colleague's test script consumes a slot.
Verify port 8193 end to end
Test with a plain TCP connect before involving the library — it separates a network problem from a FOCAS problem.

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