Limitations of packet capture

You must be aware of certain limitations of packet capture.


In the Library Manager, Application page, the Default Network Device field must be set to a physical interface.

Packet capture basics

Packet capture refers to the interception of a data packet as it travels across a network. Packet capture (as opposed to using an External Proxy Server) is an option when setting the Recording mode for the following transports:
  • TCP
  • FIX
  • HTTP
Packet capture requires specialized software:
  • On Windows systems, Network Packet Capture is included in the HCL OneTest™ API installation program. If necessary, you can rerun IBM® Installation Manager to add Network Packet Capture to the installation. See Installing HCL OneTest™ API.
  • On non-Windows systems, libpcap is typically installed by default. If necessary, you can download the latest package from

If you choose Packet Capture as your Recording mode, HCL OneTest™ API calls the appropriate packet capture software automatically.


Although packet capture is simpler than using an external proxy server, be aware of the following limitations:
  • Your system administrator might not allow the use of packet capture software due to security concerns with intercepting traffic.
  • On non-Windows systems, root permissions are required to access the network port in promiscuous mode, and thus to run packet capture.
  • Packet capture does not work with wireless network adapters. Make sure that the Default Network Device in Library Manager is set to a physical interface.
  • You can record only those messages that are sent from, or received by, the system running HCL OneTest™ API. You cannot record messages between remote systems.
  • Packet capture cannot access messages that are sent locally on a Windows system, because these messages go through the internal loopback connector. For more information about the internal loopback connector, see