How Asynchronous Functions Differ from Synchronous Functions

For a list of protocols that support asynchronous communication, see Protocol Support for Async, IPv6, and 64-bit Recording.

The Function Reference includes several functions that enable Vuser scripts to emulate asynchronous communication. These asynchronous functions differ from the other API functions in the following ways:

  • The network traffic that the asynchronous functions generate runs in parallel – simultaneously – with the main flow in the Vuser script. This means that the asynchronous communication can continue even when the synchronous steps end.
  • The asynchronous communication continues even during execution of non-web functions (e.g. lr_think_time).
  • Some of the asynchronous communication API functions use callback functions. The user needs to specify callbacks that are scheduled by the replay engine when a predefined event occurs. For details on using callbacks with asynchronous functions, see Implementing Callbacks.

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