CLIENT* clnt_create(char* host, unsigned long prog, unsigned long vers, char* proto); // for square example CLIENT* clnt_handle; clnt_handle = clnt_create(rpc_host_name, SQUARE_PROG, SQURE_VERS, "tcp");
CLIENT type
– client handle
– status error, authentication…
XDR Data Types
Default Types
-char, byte, int, float…
Additional XDR types
-const(#define), hyper(64-bit integer), guadruple(128-bit float), opaque(~c byte)
– uninterpreted binary data
Fixed length array
– e.g., int data[80]
Variable length array
– e.g., int data<80> => translate into a data structure with “len” and “val” fields
except for strings
– string line<80> => c pointer to char
– stored in memory as a normal null-terminated string
– encoded for (transmission) as a pair of length and data
XDR Routines
marshalling/unmarshalling
-found in square_xdr.c
Clean-up
-xdr.free()
-user_define.freeresult procedure
-e.g., square_prog_1_freeresult
-called after result returned
RPC header
-service procedure ID, version number, request ID…
Actual data
– arguments or results
– encoded into a byte stream depending on data type
XDR IDL + the encoding
– i.e., the binary representation of data “on-the-wire”
XDR Encoding Rules
– all data types are encoded in multiples of 4 bytes
– big endian is the transmission standard
