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Troubleshooting

Using Wireshark to Analyze OPC UA Binary Protocol

This section describes how to use Wireshark for OPC UA protocol analyzing.

First you need to install Wireshark. The source code as well as binary installers for Windows and Mac OS X are available at http://www.wireshark.org/download.html.

How to Use Wireshark

To use Wireshark, follow these steps:

  • install Wireshark and follow the on-screen instructions
  • start Wireshark
  • configure the Protocol Preferences (add Ports you want to capture)
  • select your network card
  • configure the Capture Filter
  • start capturing

If you now start your OPC UA Server and connect with your Client, you will capture all service calls on the network. After performing the actions you want to capture, stop the Wireshark capturing. You can now set “Display Filters” to reduce the view and all the captured information.

Example

First set the OPC UA ports you want to capture by setting the Wireshark Preferences. Choose “Edit” → “Preferences” from the menu. Select “Protocols” from the tree and scroll down to OpcUa. Enter all the ports you need separated by a comma (see screenshot) and confirm with “Apply”.

wireshark1.png
Set Port Numbers

Click on “Capture Options” in the main window.

wireshark5.png
Capture Options

If necessary, select the network interface for capturing.

To reduce the amount of data collected, set a capture filter to “tcp” or a specific port, e.g. “tcp port 4841” (see screenshot), and start capturing by clicking on “Start”. Then perform the actions you want to capture.

wireshark2.png
Set Capture Filter

The result is displayed in the main window having three horizontal sections. The first upper section shows the individual telegram including timestamp and direction (source to destination). To show only OPC UA related packages, enter “opcua” at “Filter”. On selecting a certain message its content is expanded in the window below. In the example you can see a response sent from the server to the client that was returned on a call of the Browse Service. The content of all objects can be decoded. In addition, the lowest window pane shows the hexadecimal view for the selected item.

wireshark3.png
Decoded Browse Response

Wireshark Issue: Lots of Checksum Errors due to TCP Checksum Offloading

When using a newer network interface card, you may notice a lot of checksum errors while capturing (see the following screenshot) caused by TCP checksum offloading (see the Wireshark wiki for more information).

wireshark-tcpoffloading-error.png
TCP Offloading Error

To suppress these errors, you have to disable TCP checksum validation. Choose “Edit” → “Preferences” from the menu, select “Protocols” → “TCP” from the tree and uncheck the box at “Validate the TCP checksum if possible” (see screenshot).

wireshark-tcpoffloading-config.png
Disable TCP Checksum Validation

Using the Trace Functionality

The SDK comes with a built-in tracing mechanism. Enabling the trace and setting the trace level is possible when initializing the UA stack. The OpcUa_ProxyStubConfiguration structure passed into UaBase_Module_InitializeUaStack offers parameters that modify the trace:

OpcUa_ProxyStubConfiguration proxyStubConfiguration;
/* Enable the trace */
proxyStubConfiguration.bProxyStub_Trace_Enabled = OpcUa_True;
/* Set the trace level */
proxyStubConfiguration.uProxyStub_Trace_Level = OPCUA_TRACE_OUTPUT_LEVEL_ERROR;
UaBase_Module_InitializeUaStack(&g_hProxyStubPlatformLayer, &proxyStubConfiguration);

In your code you can also trace into the SDK trace by including <opcua_trace.h> and calling OpcUa_Trace, e.g.:

OpcUa_Trace(OPCUA_TRACE_LEVEL_INFO, "This is a sample trace on trace level INFO\n");

There are several functions to configure the trace at runtime (see UaBaseTrace). It is possible to trace to the console (UaBase_ConsoleTrace_Enable) and to a file (UaBase_FileTrace_Enable).

In addition, you need following functions:

  • OpcUa_Trace_Toggle to activate or deactivate the trace output during runtime.
  • OpcUa_Trace_ChangeTraceLevel to set the trace level

When using configuration files (see UaBaseSettings), the functions UaClient_Settings_GetConfigurationFromSettings and UaServer_Settings_GetConfigurationFromSettings use the function UaBase_Trace_GetTraceConfigFromSettings to get the trace configuration from the configuration file.