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在查看libc6-dev軟件包提供的工具（用 dpkg -L libc6-dev 命令）的時候，發現此軟件包提供了一個有用的工具rpcgen命令。
通過rpcgen的man手冊看到此工具的作用是把RPC源程序編譯成C語言源程序，從而輕鬆實現遠程過程調用。
下面的例子程序的作用是客戶端程序取中心服務器上時間的，編程過程如下：
先編寫一個 “ RPC 語言 ” ( RPC Language ( Remote Procedure Call Language ) ) 的源文件 test.x ，文件後綴名爲 x 。
源代碼如下：
| program TESTPROG { version VERSION { string TEST(string) = 1; } = 1; } = 87654321; |
運行這個命令：
| rpcgen test.x |
| test_clnt.c test.h test_svc.c |
| /* * 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); } |
源文件test.h內容如下：
| /* * 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 */ |
源文件test_svc.c內容如下：
| /* * 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 */ } |
運行下列命令生成一個客戶端源文件test_client.c：
| rpcgen -Sc -o test_client.c test.x |
| /* * 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); } |
| rpcgen -Ss -o test_srv_func.c test.x |
| /* * 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; } |
至此，我們就可以編譯生成程序來運行了。
用下面的命令編譯生成服務端程序test_server：
| 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 |
| ./test_server |
| ./test_client 127.0.0.1 |
下面我們先給服務端程序加上代碼，使這個服務器能完成一定的工作。即修改 test_srv_func.c ，在 “ * insert server code here ” 後面加上取時間的代碼，即修改後的 test_srv_func.c 代碼如下：
| /* * 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, "服務器當前時間是 :%s", ctime(&rawtime)); result = tmp_char; return &result; } |
| 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 */ } |
| 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 |
| ./test_client 127.0.0.1 收到消息 ... 服務器當前時間是 :Tue Feb 27 11:45:21 2007 |
| rpcgen -Sm test.x > Makefile |
| # 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) |
| # 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) *~ |