Linux下C语言远程调用.doc

Linux下C语言编程的-RPC远程调用编程在查看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 /* 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 #ifdef _cplusplusextern C #endif#define TESTPROG 87654321#define VERSION 1#if defined(_STDC_) | defined(_cplusplus)#define TEST 1extern 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 1extern 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 #include #include #include #include #include #include #ifndef SIG_PF#define SIG_PF void(*)(int)#endifstatic voidtestprog_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;intmain (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.hvoidtestprog_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 */intmain (int argc, char *argv) char *host; if (argc 2) printf (usage: %s server_hostn, argv0); exit (1); host = argv1; 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.hchar *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 #include test.hchar *test_1_svc(char *argp, struct svc_req *rqstp) static char * result; static char tmp_char128; 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：voidtestprog_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 timen, host); exit(1); printf(收到消息 . %sn, *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.cgcc -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# ParametersCLIENT = test_clientSERVER = test_serverSOURCES_CLNT.c = SOURCES_CLNT.h = SOURCES_SVC.c = SOURCES_SVC.h = SOURCES.x = test.xTARGETS_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 += -lnslRPCGENFLAGS = # 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# ParametersCLIENT = test_clientSERVER = test_serverSOURCES_CLNT.c = SOURCES_CLNT.h = SOURCES