linux RPC

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在查看libc6-dev软件包提供的工具（用 dpkg -L libc6-dev 命令）的时候，发现此软件包提供了一个有用的工具rpcgen命令。
通过rpcgen的man手册看到此工具的作用是把RPC源程序编译成C语言源程序，从而轻松实现远程过程调用。
下面的例子程序的作用是客户端程序取中心服务器上时间的，编程过程如下：
先编写一个 “ RPC 语言 ” ( RPC Language ( Remote Procedure Call Language ) ) 的源文件 test.x ，文件后缀名为 x 。
源代码如下：

program TESTPROG {    version VERSION {      string TEST(string) = 1;    } = 1; } = 87654321;

说明：这里数字87654321是RPC程序编号，还有VERSION版本号为1，都是给RPC服务程序用的。同时指定程序接受一个字符串参数。

运行这个命令：

rpcgen test.x

将生成三个源文件：

test_clnt.c  test.h  test_svc.c

源文件test_clnt.c 内容如下：

/*  * Please do not edit this file.  * It was generated using rpcgen.  */ #include <memory.h> /* for memset */ #include "test.h" /* Default timeout can be changed using clnt_control() */ static struct timeval TIMEOUT = { 25, 0 }; char ** test_1(char **argp, CLIENT *clnt) {         static char *clnt_res;         memset((char *)&clnt_res, 0, sizeof(clnt_res));         if (clnt_call (clnt, TEST,                 (xdrproc_t) xdr_wrapstring, (caddr_t) argp,                 (xdrproc_t) xdr_wrapstring, (caddr_t) &clnt_res,                 TIMEOUT) != RPC_SUCCESS) {                 return (NULL);         }         return (&clnt_res); }

说明：这是一个客户端调用函数，即客户端代码需要用到此函数。

源文件test.h内容如下：

/*  * Please do not edit this file.  * It was generated using rpcgen.  */ #ifndef _TEST_H_RPCGEN #define _TEST_H_RPCGEN #include <rpc/rpc.h> #ifdef __cplusplus extern "C" { #endif #define TESTPROG 87654321 #define VERSION 1 #if defined(__STDC__) || defined(__cplusplus) #define TEST 1 extern  char ** test_1(char **, CLIENT *); extern  char ** test_1_svc(char **, struct svc_req *); extern int testprog_1_freeresult (SVCXPRT *, xdrproc_t, caddr_t); #else /* K&R C */ #define TEST 1 extern  char ** test_1(); extern  char ** test_1_svc(); extern int testprog_1_freeresult (); #endif /* K&R C */ #ifdef __cplusplus } #endif #endif /* !_TEST_H_RPCGEN */

说明：这里定义了一些公用头文件。

源文件test_svc.c内容如下：

/*  * Please do not edit this file.  * It was generated using rpcgen.  */ #include "test.h" #include <stdio.h> #include <stdlib.h> #include <rpc/pmap_clnt.h> #include <string.h> #include <memory.h> #include <sys/socket.h> #include <netinet/in.h> #ifndef SIG_PF #define SIG_PF void(*)(int) #endif static void testprog_1(struct svc_req *rqstp, register SVCXPRT *transp) {         union {                 char *test_1_arg;         } argument;         char *result;         xdrproc_t _xdr_argument, _xdr_result;         char *(*local)(char *, struct svc_req *);         switch (rqstp->rq_proc) {         case NULLPROC:                 (void) svc_sendreply (transp, (xdrproc_t) xdr_void, (char *)NULL);                 return;         case TEST:                 _xdr_argument = (xdrproc_t) xdr_wrapstring;                 _xdr_result = (xdrproc_t) xdr_wrapstring;                 local = (char *(*)(char *, struct svc_req *)) test_1_svc;                 break;         default:                 svcerr_noproc (transp);                 return;         }         memset ((char *)&argument, 0, sizeof (argument));         if (!svc_getargs (transp, (xdrproc_t) _xdr_argument, (caddr_t) &argument)) {                 svcerr_decode (transp);                 return;         }         result = (*local)((char *)&argument, rqstp);         if (result != NULL && !svc_sendreply(transp, (xdrproc_t) _xdr_result, result)) {                 svcerr_systemerr (transp);         }         if (!svc_freeargs (transp, (xdrproc_t) _xdr_argument, (caddr_t) &argument)) {                 fprintf (stderr, "%s", "unable to free arguments");                 exit (1);         }         return; } int main (int argc, char **argv) {         register SVCXPRT *transp;         pmap_unset (TESTPROG, VERSION);         transp = svcudp_create(RPC_ANYSOCK);         if (transp == NULL) {                 fprintf (stderr, "%s", "cannot create udp service.");                 exit(1);         }         if (!svc_register(transp, TESTPROG, VERSION, testprog_1, IPPROTO_UDP)) {                 fprintf (stderr, "%s", "unable to register (TESTPROG, VERSION, udp).");                 exit(1);         }         transp = svctcp_create(RPC_ANYSOCK, 0, 0);         if (transp == NULL) {                 fprintf (stderr, "%s", "cannot create tcp service.");                 exit(1);         }         if (!svc_register(transp, TESTPROG, VERSION, testprog_1, IPPROTO_TCP)) {                 fprintf (stderr, "%s", "unable to register (TESTPROG, VERSION, tcp).");                 exit(1);         }         svc_run ();         fprintf (stderr, "%s", "svc_run returned");         exit (1);         /* NOTREACHED */ }

说明：这是一个标准的服务器端代码。

运行下列命令生成一个客户端源文件test_client.c：

rpcgen -Sc -o test_client.c test.x

源代码test_client.c如下：

/*  * This is sample code generated by rpcgen.  * These are only templates and you can use them  * as a guideline for developing your own functions.  */ #include "test.h" void testprog_1(char *host) {         CLIENT *clnt;         char * *result_1;         char * test_1_arg; #ifndef DEBUG         clnt = clnt_create (host, TESTPROG, VERSION, "udp");         if (clnt == NULL) {                 clnt_pcreateerror (host);                 exit (1);         } #endif  /* DEBUG */         result_1 = test_1(&test_1_arg, clnt);         if (result_1 == (char **) NULL) {                 clnt_perror (clnt, "call failed");         } #ifndef DEBUG         clnt_destroy (clnt); #endif   /* DEBUG */ } int main (int argc, char *argv[]) {         char *host;         if (argc < 2) {                 printf ("usage: %s server_host/n", argv[0]);                 exit (1);         }         host = argv[1];         testprog_1 (host); exit (0); }

运行这个命令生成服务端源文件test_srv_func.c：

rpcgen -Ss -o test_srv_func.c test.x

源文件test_srv_func.c内容如下：

/*  * This is sample code generated by rpcgen.  * These are only templates and you can use them  * as a guideline for developing your own functions.  */ #include "test.h" char ** test_1_svc(char **argp, struct svc_req *rqstp) {         static char * result;         /*          * insert server code here          */         return &result; }

说明：这是一个服务器端调用的函数。

至此，我们就可以编译生成程序来运行了。
用下面的命令编译生成服务端程序test_server：

gcc -Wall -o test_server test_clnt.c test_srv_func.c test_svc.c

用下面的命令编译生成客户端程序test_client：

gcc -Wall -o test_client test_client.c test_clnt.c

运行下列命令启动服务端：

./test_server

运行下列命令可以进行客户端测试：

./test_client 127.0.0.1

但是由于现的的服务端没有处理客户端请求，所以这样的程序还不能完成任何工作。

下面我们先给服务端程序加上代码，使这个服务器能完成一定的工作。即修改 test_srv_func.c ，在 “ * insert server code here ” 后面加上取时间的代码，即修改后的 test_srv_func.c 代码如下：

/*  * This is sample code generated by rpcgen.  * These are only templates and you can use them  * as a guideline for developing your own functions.  */ #include <time.h> #include "test.h" char ** test_1_svc(char **argp, struct svc_req *rqstp) {         static char * result;         static char tmp_char[128];         time_t rawtime;         /*          * insert server code here          */         if( time(&rawtime) == ((time_t)-1) ) {                 strcpy(tmp_char, "Error");                 result = tmp_char;                 return &result;         }         sprintf(tmp_char, "服务器当前时间是 :%s", ctime(&rawtime));         result = tmp_char;         return &result; }

再修改客户端代码以显示服务器端返回的内容，即修改test_client.c源文件，只需要修改其中的函数testprog_1，修改后如下：

void testprog_1(char *host) {         CLIENT *clnt;         char * *result_1;         char * test_1_arg;         test_1_arg = (char *)malloc(128); #ifndef DEBUG         clnt = clnt_create (host, TESTPROG, VERSION, "udp");         if (clnt == NULL) {                 clnt_pcreateerror (host);                 exit (1);         } #endif  /* DEBUG */         result_1 = test_1(&test_1_arg, clnt);         if (result_1 == (char **) NULL) {                 clnt_perror (clnt, "call failed");         }         if (strcmp(*result_1, "Error") == 0) {                 fprintf(stderr, "%s: could not get the time/n", host);                 exit(1);         }         printf("收到消息 ... %s/n", *result_1); #ifndef DEBUG         clnt_destroy (clnt); #endif   /* DEBUG */ }

重新运行上述编译命令编译生成程序：

gcc -Wall -o test_server test_clnt.c test_srv_func.c test_svc.c gcc -Wall -o test_client test_client.c test_clnt.c

启动服务端程序后运行客户端程序如下：

./test_client 127.0.0.1 收到消息 ... 服务器当前时间是 :Tue Feb 27 11:45:21 2007

为了省略每次输入gcc命令的麻烦，也为了维护我们的工程，可以运行下列命令生成一个Makefile文件：

rpcgen -Sm test.x > Makefile

生成的Makefile内容如下：

# This is a template Makefile generated by rpcgen # Parameters CLIENT = test_client SERVER = test_server SOURCES_CLNT.c = SOURCES_CLNT.h = SOURCES_SVC.c = SOURCES_SVC.h = SOURCES.x = test.x TARGETS_SVC.c =       TARGETS_CLNT.c =       TARGETS =            OBJECTS_CLNT = $(SOURCES_CLNT.c:%.c=%.o) $(TARGETS_CLNT.c:%.c=%.o) OBJECTS_SVC = $(SOURCES_SVC.c:%.c=%.o) $(TARGETS_SVC.c:%.c=%.o) # Compiler flags CFLAGS += -g LDLIBS += -lnsl RPCGENFLAGS = # Targets all : $(CLIENT) $(SERVER) $(TARGETS) : $(SOURCES.x)         rpcgen $(RPCGENFLAGS) $(SOURCES.x) $(OBJECTS_CLNT) : $(SOURCES_CLNT.c) $(SOURCES_CLNT.h) $(TARGETS_CLNT.c) $(OBJECTS_SVC) : $(SOURCES_SVC.c) $(SOURCES_SVC.h) $(TARGETS_SVC.c) $(CLIENT) : $(OBJECTS_CLNT)         $(LINK.c) -o $(CLIENT) $(OBJECTS_CLNT) $(LDLIBS) $(SERVER) : $(OBJECTS_SVC)         $(LINK.c) -o $(SERVER) $(OBJECTS_SVC) $(LDLIBS)  clean:          $(RM) core $(TARGETS) $(OBJECTS_CLNT) $(OBJECTS_SVC) $(CLIENT) $(SERVER)

由于我们手工生成了源文件，所以要修改一下这个Makefile，修改后如下：

# This is a template Makefile generated by rpcgen # Parameters CLIENT = test_client SERVER = test_server SOURCES_CLNT.c = SOURCES_CLNT.h = SOURCES_SVC.c = SOURCES_SVC.h = SOURCES.x = test.x TARGETS_SVC.c = test_clnt.c test_srv_func.c test_svc.c TARGETS_CLNT.c = test_clnt.c test_client.c TARGETS = test.h   test_clnt.c test_svc.c    OBJECTS_CLNT = $(SOURCES_CLNT.c:%.c=%.o) $(TARGETS_CLNT.c:%.c=%.o) OBJECTS_SVC = $(SOURCES_SVC.c:%.c=%.o) $(TARGETS_SVC.c:%.c=%.o) # Compiler flags CFLAGS += -g LDLIBS += -lnsl RPCGENFLAGS = # Targets all : $(CLIENT) $(SERVER) $(TARGETS) : $(SOURCES.x)         rpcgen $(RPCGENFLAGS) $(SOURCES.x) $(OBJECTS_CLNT) : $(SOURCES_CLNT.c) $(SOURCES_CLNT.h) $(TARGETS_CLNT.c) $(OBJECTS_SVC) : $(SOURCES_SVC.c) $(SOURCES_SVC.h) $(TARGETS_SVC.c) $(CLIENT) : $(OBJECTS_CLNT)         $(LINK.c) -o $(CLIENT) $(OBJECTS_CLNT) $(LDLIBS) $(SERVER) : $(OBJECTS_SVC)         $(LINK.c) -o $(SERVER) $(OBJECTS_SVC) $(LDLIBS) clean:         $(RM) core $(TARGETS) $(OBJECTS_CLNT) $(OBJECTS_SVC) $(CLIENT) $(SERVER) *~