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.