When a client application connects to a Web service running on an vSphere server (ESX/ESXi or vCenter Server system), the server detects the version of the API that was used to develop the client and makes available only those operations supported by the client.
Client applications convey information about the API version used in the SOAP messages that they send to a vSphere server. These SOAP messages include a
versionID in the
soapAction attribute. The details are handled transparently by the SOAP toolkit and the client proxy code. The server adjusts its behavior based on the client’s version information, exposing the API version that the client supports to the client.
If you are developing a client application that must support multiple server versions at the same time (ESX/ESXi 5.0 and ESX/ESXi 3.x, for example), you must obtain information about the API versions that are supported on the server and provide logic in your code to use or not use features, based upon the version information.