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One of the reasons the remote framework currently uses XML-RPC for its transfer protocol is that XML-RPC provides many of the network transfer protocol requirements as-is. Readers are encouraged to familiarize themselves with the XML-RPC specification before reading this section.

Administrative methods

Remote calls to the administrative methods are encoded as standard XML-RPC function requests. The name of the administrative method is used as the name of the XML-RPC function, and the remote method's parameter array is encoded as the XML-RPC parameter list. The remote method can be expected to return a single value, which will be deserialized into the logical type model as defined by the XML-RPC specification.

Dispatched methods

Calling a dispatched method is slightly more involved than calling an administrative method, and is therefore handled slightly differently. For one, calling a dispatched method requires a valid connection as set up by the createSession administrative method. Since XML-RPC connections are stateless, this creates the need for an extra, implicit parameter for each dispatched method call. (This extra parameter informs the data server which active connection is making the requested call.) Further, since the namespace for administrative and dispatched methods are distinct, we cannot call a dispatched method directly without the possibility of a namespace clash between the two types of methods.

For all of these reasons, dispatched method calls are made with the special dispatch XML-RPC function name. The first two elements of the XML-RPC parameter list are, respectively, the session key of the active connection (returned by the createSession method), and the name of the dispatched method to execute. The parameters to the dispatched method are then encoded as the remaining XML-RPC parameters, in order.

As with administrative methods, the caller can expect the result to be a single value, which can be translated into the logical type model as defined by the XML-RPC specification.


Null values

The XML-RPC does not define a way to represent null values in an XML-RPC request or response. Since the logical type model includes null values, we need a way of representing them in an XML-RPC stream. We do so by using a special string value: "*([-NULL-])*". All client libraries using the XML-RPC transport protocol should encode null values as this string, and should turn any instances of this string they see into a null value.

You might be asking yourself, what if I need to send the string "*([-NULL-])*"? Unfortunately, you are currently out of luck.

Integer values

The XML-RPC specification states that integer XML-RPC values are limited to 32 bits. As stated in the logical type model, this means that you cannot use the XML-RPC transport protocol to call remote methods which require an integer of a larger size.

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