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No Tag Data via TCP using Ethernet-To-Serial Converter


Last Update: 11/12/2018

Channel Diagnostics can display basic information about a TCP connection to an Ethernet-to-Serial converter. The window may show one of three states: no TX or RX bytes, green (TX) text only, or both green (TX) and white (RX) text.

  • No TX or RX bytes means that the server cannot make a TCP socket connection to the Ethernet-to-Serial converter. This state will occur if no client attempts to access the device in question. If the Channel Diagnostics window's "Failed reads" or "Failed writes" are increasing within the amount of time specified in the Timing device property, then a client is connected. If the Channel Diagnostics window's "Failed reads" or "Failed writes" are not increasing, then there is no client connected. Before troubleshooting further, connect a client to the device in question. Suggestions for the "No TX or RX bytes" state are as follows:
    • Can you ping the converter? If not, the server will not be able to connect. Verify that the PC and converter are in the same IP subnet or that there is a gateway that can forward packets between the two subnets.
    • Are all the converter's available connections in use? Since most applications cannot share a serial port, a typical converter only allows one Ethernet connection per physical serial port.
    • Is a firewall blocking access to the TCP port that the driver is attempting to use?

      Note: This state normally does not apply to UDP. Since UDP is connectionless, the server can transmit a UDP message even if there is no device to receive it.
  • Green (TX) text only means that the server can send data to the converter, but that the end device does not send anything back. Make sure that the driver has been set to use the correct TCP port on the converter. This is usually a "raw" port, not one used for a COM-port redirector or for Telnet.
  • Both green (TX) and white (RX) text means that the end device sends messages back, but there is still something that prevents access to the tags. Look in the server's Event Log for any error codes that the device might be returning. Then, verify that the driver settings and PLC/device are set properly by referring to the driver's product manual for more information.

See Also: Channel Diagnostics Guide

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