From Xojo Documentation

Property (As Boolean )
aHTTPSocket.Yield = newBooleanValue
BooleanValue = aHTTPSocket.Yield

New in 5.5

Supported for all project types and targets.

When you are using synchronous HTTP, your application may need to wait a noticeable amount of time to get or post a page. Setting Yield to True allows for events and other code to execute while waiting for a page.

Yield is relevant when you pass the optional Timeout parameter with Get or GetHeaders. Set Yield to True just prior to a call to any of these methods.