a_rpcLab

Wind River Systems Tornado Training Workshop © Copyright Wind River Systems F -15RPC AppendixRPC LabThe RPC programming lab is unsupported.Remote Procedure Call (RPC) Objective:To be able to call functions on remote nodes using the RPC protocol.In a X window, change your directory to HomeDir/unsupported/ rpc. In this directory there is a program which runs on UNIX and prints the date.%unixDateFri Dec 27 06:35:31 1991This exercise is to modify this program so that, using RPC, we can execute the code from VxWorks. The steps below provide an overview of what is required. These steps will be discussed in more detail later.1.Remake VxWorks with RPC included.2.Create time.x, a RPC specifications file. To keep everyone’swork separate, use the following RPC program number: Team Program Number10x2000000120x2000000230x20000003......80x200000083.Write unixTimeServer.c (a modification of unixDate.c) to actas a RPC server.4.Write vxTimeClient.c to act as an RPC client.e rpcgen on time.x to generate the time.h, time_svc.c andtime_clnt.c files.6.Modify time.h so that it will compile for VxWorks. You mayuse the script provided:%rpcModify time.h(Note: this step is optional if you compile with -nostdinc.)pile and link unixTimeServer.c and time_svc.c intotimeServer. Since timeServer will run on the host side, use the native compiler for your host (cc in the laboratory). You may want to compile unixTimeServer.c with a native ANSIcompiler, and time_svc.c with a traditional compiler, then link the resulting object modules. Run timeServer in background.pile vxTimeClient.c and time_clnt.c. Since the client runsunder VxWorks, use the appropriate cross-compiler for your target.9.Incrementally link vxTimeClient.o and time_clnt.o to create afile called timeClient.o. Use the cross-linker for yourarchitecture.10.Load timeClient.o on your VxWorks target and test it.You can either stop here and start the lab or you can continue reading for a more detailed description of each of the steps above. Do what you think will make best use of your lab time.1.Modify config.h so that the symbol INCLUDE_RPC is defined, oruse WindConfig. Remake the system image. Then reboot your target.2.Creating time.x, the RPC specification fileThe RPC specification file has the following format:program PROG_NAME {version VERSION_NAME {type routineName (type) = 1;type routineName (type) = 2;...} =versionNumber;} =programNumber;The PROG_NAME and VERSION_NAME are arbitrary names that will be converted by rpcgen into symbolic constants. We’ll call them TIME_PROG and TIME_VERS respectively. Since this is our first version, we’ll assign versionNumber to be 1. The program number must be in the range 0x200000000 to 0x3ffffff. Other numbers are reserved by Sun. Use a program number of0x2000000n where n is your team number (0-8). Now we have: program TIME_PROG {version TIME_VERS {type routineName (type) = 1;type routineName (type) = 2;...} = 1;T eam 1 program number shown } = 0x20000001;The innermost part of the structure is just a list of the routines in your program. We only have one routine, let’s call itprint_time. By convention, the program name is written inupper case. So we have:program TIME_PROG {version TIME_VERS {type PRINT_TIME (type) = 1;} = 1;} = 0x20000001;What are we going to pass as an argument to print_time?Nothing, so it is type void. What does print_time return? A pointer to a character (string). RPC has predefined term,string, for a NULL terminated character string. So, now we have:program TIME_PROG {version TIME_VERS {string PRINT_TIME (void) = 1;} = 1;} = 0x20000001;3.Modify unixDate.cCopy unixDate.c to unixTimeServer.c. We will make ourchanges in unixTimeServer.cRemove the main() routine. The time_svc.c generated byrpcgen has the program’s main().As a local routine print_time returns a pointer to a character (a string). Remote calls always use one more level of indirection than you would locally, i.e. if the local routine passes (orreturns) a long, the remote call uses a pointer to a long. So,print_time must return a pointer to a string, i.e. “char **”.The name of the routine,PRINT_TIME, described in thespecification file is converted to lower case and appended with the version number. That is, if you have a routine name ofBLAH_BLAH in the specifications file and your version number is 2, then you need to define a routine called blah_blah_2. For our purposes, we need to changed the name of the routinefrom print_time to print_time_1. So, the declaration should now read:char ** print_time_1 ()Lastly, we need to modify the return value from:return (pStr);— return a character pointer — to:return (&pStr);returning a pointer to a string.4.Write a routine called printTime in a file called vxTimeClient.c:This routine must call:q rpcTaskInit ()Initializes the VxWorks RPCpackage for this taskq clnt_create ()Creates a client handle to the RPCtask on the remote host. TheCLIENT handle returned fromthis routine should be stored in aglobal variable. By only callingclnt_create if the global variableis NULL, you avoid establishingthis handle every time printTimeis called. Note, however, that theCLIENT handle may not beshared between tasks. If youintend to call printTime() directlyfrom the Wind Shell, you mustrecreate (and later delete, withclnt_destroy) the client handle oneach call, as in this case a newtask is created for each call. Youmight define a macro and useconditional compilation to treatthese two cases differently.Another possible solution isgiven in the lab answers.q print_time_1 ()Gets the time from the server task q printf ()Prints the string received fromprint_time_1q free()Free memory allocated for thestring.5.Call rpcgen.%rpcgen time.xThis should create a time.h,time_clnt.c, and time_svc.c.6.Call rpcModify.%rpcModify time.hThis changes the include line in time.h from#include <rpc/rpc.h>to#ifdef VXWORKS#include “vxWorks.h”#include “rpc/rpc.h”#else#include <rpc/rpc.h>#endifIf VXWORKS is defined,vxWorks.h and rpc/rpc.h will beincluded, otherwise rpc/rpc.h (under/usr/include).pile and link the server program with:%cc unixTimeServer.c time_svc.c-o timeServerStart the server program.%./timeServerpile the main client program and client stub:%ccx -DVXWORKS vxTimeClient.c%ccx -traditional -DVXWORKS time_clnt.cThe “-traditional” flag is required because rpcgen generates non-ANSI code. The “-DVXWORKS” is to define VXWORKS so that the correct header files will be included in time.h. 9.Link the client modules to form a client program:%ld Arch-r vxTimeClient.o time_clnt.o\-o timeClient.o10.From VxWorks, change directory to HomeDir/unsupported/rpc and load the client module:->ld < timeClient.ovalue = 0 = 0x0Call the printTime routine (It was defined in client.o).->printTimeFri Dec 27 14:36:09 1991Output from remote routine value = 0 = 0x0。