rpcgen is a tool that generates C code to implement an RPC protocol. The input to
rpcgen is a language similar to C known as RPC Language (Remote Procedure Call Language).
rpcgen is normally used as in the first synopsis where it takes an input file and generates up to four output files. If the
infile is named
proto.x, then
rpcgen will generate a header file in
proto.h, XDR routines in
proto_xdr.c, server-side stubs in
proto_svc.c, and client-side stubs in
proto_clnt.c. With the
-T option, it will also generate the RPC dispatch table in
proto_tbl.i. With the
-Sc option, it will also generate sample code which would illustrate how to use the remote procedures on the client side. This code would be created in
proto_client.c. With the
-Ss option, it will also generate a sample server code which would illustrate how to write the remote procedures. This code would be created in
proto_server.c.
The server created can be started both by the port monitors (for example,
inetd or
listen) or by itself. When it is started by a port monitor, it creates servers only for the transport for which the file descriptor 0 was passed. The name of the transport must be specified by setting up the environmental variable
PM_TRANSPORT. When the server generated by
rpcgen is executed, it creates server handles for all the transports specified in
NETPATH environment variable, or if it is unset, it creates server handles for all the visible transports from
/etc/netconfig file.
Note: the transports are chosen at run time and not at compile time. When the server is self-started, it backgrounds itself by default. A special define symbol
RPC_SVC_FG can be used to run the server process in foreground.
The second synopsis provides special features which allow for the creation of more sophisticated RPC servers. These features include support for user provided
#defines and RPC dispatch tables. The entries in the RPC dispatch table contain:
+
pointers to the service routine corresponding to that procedure,
+
a pointer to the input and output arguments,
+
the size of these routines
A server can use the dispatch table to check authorization and then to execute the service routine; a client library may use it to deal with the details of storage management and XDR data conversion.
The other three synopses shown above are used when one does not want to generate all the output files, but only a particular one. Some examples of their usage is described in the
EXAMPLES section below. When
rpcgen is executed with the
-s option, it creates servers for that particular class of transports. When executed with the
-n option, it creates a server for the transport specified by
netid. If
infile is not specified,
rpcgen accepts the standard input.
The C preprocessor,
cpp(1) is run on the input file before it is actually interpreted by
rpcgen For each type of output file,
rpcgen defines a special preprocessor symbol for use by the
rpcgen programmer:
RPC_HDR
defined when compiling into header files
RPC_XDR
defined when compiling into XDR routines
RPC_SVC
defined when compiling into server-side stubs
RPC_CLNT
defined when compiling into client-side stubs
RPC_TBL
defined when compiling into RPC dispatch tables
Any line beginning with ‘%' is passed directly into the output file, uninterpreted by
rpcgen.
For every data type referred to in
infile rpcgen assumes that there exists a routine with the string “xdr_” prepended to the name of the data type. If this routine does not exist in the RPC/XDR library, it must be provided. Providing an undefined data type allows customization of XDR routines.