DOP-W127B: Ping Success Is IP Reachability, Not Transfer

The operator can ping the DOP-W127B, but a project upload reports ethernet cant be opened. Trying COM2 reports no response, and both Ethernet connectors appear to behave the same way. That combination points to transfer-session setup or interface selection, not proof of a failed network link or damaged project.

What is the screen telling you?

A successful ping answers one narrow question: an IP endpoint replied to an ICMP echo request. It does not prove that the project-transfer software can open its required application session, that the reply came from the intended HMI, or that the selected HMI interface accepts the requested operation.

This failure occurs before runtime tag processing. A tag, driver, or controller binding cannot cause the transfer client itself to fail to open Ethernet. Establish a project-transfer session first; troubleshoot tags and controller communications only after the project can be transferred or opened.

Which connection path should you test first?

The installation presents three candidates: LAN1, LAN2, and COM2. Test them independently. Switching between incomplete Ethernet and serial configurations creates multiple variables and hides the first failed layer.

LAN1 and LAN2 are both valid diagnostic candidates, but neither should be treated as a transparent substitute for the other. The recommended approach is to validate one Ethernet connector from end to end, then repeat the identical sequence on the other connector. This produces comparable results and reveals an interface-specific configuration error.

Why does ping work while project upload fails?

Ping and project transfer operate at different layers. Ping can succeed while the transfer application is pointed at the wrong network adapter, follows an unintended route, is blocked by host security controls, targets a duplicate IP address, or cannot establish the HMI transfer service session.

First confirm identity, not merely reachability. Disconnect the HMI Ethernet cable and ping the same address again. A continuing reply identifies another device or route answering at that address. If replies stop, reconnect the selected HMI connector and continue.

Next inspect the engineering computer's active adapters and route to the target address. Disable unrelated paths temporarily where site policy permits, or explicitly select the adapter used for the HMI network. A wireless, VPN, virtual-machine, or secondary wired interface can carry the ping differently from the transfer client's selected interface.

Host firewall or endpoint security can also distinguish between ICMP and application traffic. Test under the site's approved diagnostic policy, and restore protection after the comparison. Do not guess a TCP or UDP port number; read the transfer software or product documentation for the required service and inspect the blocked-event log for the actual executable and traffic.

How should LAN1 and LAN2 be tested separately?

1. Record the current IP address, subnet mask, gateway entry, selected transfer model, and computer network adapter. Capture the settings before changing them.
2. Connect only LAN1. Remove LAN2 from the test path so that link indication and traffic belong to one connector.
3. Confirm that the computer address belongs to the intended subnet and does not duplicate the HMI address. Use the configured subnet mask for the comparison rather than assuming an address class.
4. Ping the HMI address, then disconnect LAN1 and repeat the ping. The response must disappear when the target is disconnected.
5. Reconnect LAN1. In the project-transfer software, select the DOP-W127B target and enter the address assigned to that interface. Bind the transfer operation to the computer adapter on the same test network if the software provides that choice.
6. Attempt the project upload and record the exact message and time. If it still reports ethernet cant be opened, inspect local firewall, endpoint-security, and route diagnostics at that time.
7. Disconnect LAN1, connect only LAN2, and repeat every step with the address and settings assigned to LAN2. Do not carry an assumed LAN1 address into the LAN2 test.

If both connectors pass identity and routing checks but fail at the same transfer-opening stage, focus on the transfer software configuration, selected HMI target, computer adapter, host filtering, and HMI transfer state. Two identical errors do not by themselves prove two defective Ethernet ports.

Why does COM2 report no response?

COM2 is an independent serial path. A no response result can arise from the wrong physical interface, incorrect transmit/receive wiring, missing signal reference, mismatched serial format, wrong station selection, or using a port role that does not accept the requested transfer operation.

1. Read the configured electrical interface and communication format from the HMI settings or retained project. Do not infer them from the connector label alone.
2. Compare the cable pinout with both endpoint definitions. Check signal direction and reference conductors with power removed where required by the equipment procedure.
3. Configure the engineering interface to match the recorded serial format and target selection.
4. Monitor transmit and receive activity during one request. Transmit with no receive activity directs the check toward wiring, interface type, HMI port role, or target selection. Receive activity with rejected frames directs it toward mismatched communication settings.

The missing CDC menu item does not resolve any of these checks. Use the functions actually exposed by the installed HMI configuration and software combination.

How do you verify the fix without creating another fault?

Do not use firmware updating as the first connectivity test. Firmware work writes to the device and can introduce a second problem while the original transfer path remains unresolved. First obtain a repeatable project-transfer connection with the existing configuration.

After access is restored, compare the uploaded project's communication configuration with the live tag, driver, and controller path. The tag can be correct while its driver or device binding points elsewhere. Verify runtime values only after the transfer layer remains stable.

FAQ