readme

this gives details of the network programming

Simple RPC program that adds a variable number of integers
(sent as a variable length array).

This RPC program supports 1 remote procedure:

	vadd : adds a bunch of ints and returns the int sum.


The key to using a variable length array is to understand how such an
array is implemented by XDR. A variable length array is
encoded/decoded by first encoding/decoding the (integer) length of the
array. Next comes the array elements starting with the first (index
[0]) and so on. If we use rpcgen, we need to know what specific data
structures rpcgen expects us to use to specify both the length and the
list of array elements. This is easy - just look at the code generated
by rpcgen (all you need to look at is really the .h file). rpcgen will
define a struct for us that holds both the array length and a pointer
to the array elements. 

The client stubs produced by rpcgen will be expecting one of these structs
(a pointer to one of these structs), and the remote procedure we supply must 
take a pointer to one of these structs as an argument. For example, suppose
we want to use a variable length array of int. We need to declare a new type name:

typedef int iarray<>;

The <> means "variable length array" in XDR.

Seeing this typedef in the protocol definition file, rpcgen will create
the following:

typedef struct {
	u_int iarray_len;
	int *iarray_val;
} iarray;

In our code we need to declare function parameters as having type iarray
(or pointer to iarray). Inside our functions we need to access the fields.

Check out the code in this directory for an example. This example passes a variable
length array of ints to the remote procedure, which returns the sum.