-17 — EW_PROTOCOL — protocol error

The response did not match what the library expected — a version or framing mismatch between the Fwlib build and the controller.

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

Using a Fwlib32 build older than the controller series, or a 30i library against a 0i control.
A network device altering the stream, such as an inspecting firewall or a poorly behaved NAT.
Mixing FOCAS1 and FOCAS2 calls against a control that supports only one.

Resolution

How to fix it

Match the library to the controller series
FANUC ships different Fwlib builds per series. Using the wrong one produces -17 on calls that should work.
Remove middleboxes from the path
Deep packet inspection on port 8193 corrupts FOCAS framing.
Consider MTConnect instead
If the FOCAS version matrix is fighting you, a FANUC MTConnect adapter gives a stable, documented interface — and Forge normalizes it directly.

Normalization

What Forge does about it

This is a configuration or addressing mistake on the wire, upstream of anything Forge sees. Where Forge helps is the step after you fix it: once the point returns data, its vendor tag name maps to a canonical field automatically, so you do not also have to hand-maintain a name table for every point you just re-addressed.

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