关于“RPC语言”
RPC语言也是一种专门的编程语言,当然这里我们不需要知道太多,只需要能看懂下面这种基本结构就行了:
program TESTPROG { version VERSION { string TEST(string) = 1; } = 1; } = 87654321; |
这里TESTPROG和VERSION是两个变量,用于标识一个单独的RPC接口。这被RPC服务程序,比如portmap用到,我们可以不用关心,变量名字也是随便取的。但取值要在你的系统中是唯一的。
“string TEST(string) = 1;”这一行说明有两个函数test_VERSION和test_VERSION_svc,这里由于VERSION变量为1,所以函数名为test_1和 test_1_svc,这两个函数用于在服务器端和客户端实现调用,即:
在客户端调用test_1函数,服务器端调用test_1_svc函数处理并返回。
函数的类型是string,RPC语言中string即C里面的一个字符串。所以上述函数有一个字符串作为参数传递,同时要返回字符串。即:
char ** test_1(char **argp, CLIENT *clnt) 和 char **test_1_svc(char **argp, struct svc_req *rqstp)
同理,如果声明是这样的:
program RDICTPROG /* name of remote program ( not used ) */ { version RDICTVERS /* declaration of version ( see below ) */ { int INITW ( void ) = 1; /* first procedure in this program */ int INSERTW ( string ) = 2; /* second procedure in this program */ int DELETEW ( string ) = 3; /* third procedure in this program */ int LOOKUPW ( string ) = 4; /* fourth procedure in this program */ } = 1; /* definition of the program version */ } = 0x30090949; /* remote program number ( must be unique ) */ |
则 说明这个RPC中有四个函数可用,即客户端可以调用initw_1、insertw_1、deletew_1、lookupw_1四个函数来向服务端发送 消息,服务端可以用initw_1_svc、insertw_1_svc、deletew_1_svc、lookupw_1_svc四个函数来处理请求并 返回结果。
原任务
假设现在有这样一个程序,源代码如下:
/* dict.c -- main, initw, nextin, insertw, deletew, lookupw */ #include #include #include #include #define MAXWORD 50 /* maximum length of a command or word */ #define DICTSIZ 100 /* maximum number of entries in dictionary. */ char dict[DICTSIZ][MAXWORD + 1]; /* storage for a dictionary of words */ int nwords = 0; /* number of words in the dictionary */ /* 函数原型 */ int nextin(char *cmd, char *word); int initw(void); int insertw(const char *word); int deletew(const char *word); int lookupw(const char *word); /* ------------------------------------------------------------------ * main -- insert, delete, or lookup words in a dictionary as specified * ------------------------------------------------------------------ */ int main(int argc, char *argv[]) { char word[MAXWORD + 1]; /* space to hold word from input line */ char cmd; int wordlen; /* length of input word */ printf("Please input:\n"); while (1) { wordlen = nextin(&cmd, word); if (wordlen < 0) { exit(0); } switch (cmd) { case 'I': /* 初始化 */ initw(); printf("Dictionary initialized to empty.\n"); break; case 'i': /* 插入 */ insertw(word); printf("%s inserted.\n", word); break; case 'd': /* 删除 */ if (deletew(word)) { printf("%s deleted.\n", word); } else { printf("%s not found.\n", word); } break; case 'l': /* 查询 */ if (lookupw(word)) { printf("%s was found.\n", word); } else { printf("%s was not found.\n", word); } break; case 'q': /* 退出 */ printf("Program quits.\n"); exit(0); break; default: /* 非法输入 */ printf("command %c invalid.\n", cmd); break; } /* end of switch */ } /* end of while */ return 0; } /* end of main */ /* ------------------------------------------------------------------ * nextin -- read a command and(possibly) a word from the next input line * ------------------------------------------------------------------ */ int nextin(char *cmd, char *word) { int i, ch; ch = getc(stdin); while (isspace(ch)) { ch = getc(stdin); } /* end of while */ if (ch == EOF) { return (-1); } *cmd = (char) ch; ch = getc(stdin); while (isspace(ch)) { ch = getc(stdin); } /* end of while */ if (ch == EOF) { return (-1); } if (ch == '\n') { return (0); } i = 0; while (!isspace(ch)) { if (++i > MAXWORD) { printf("error: word too long.\n"); exit(1); } *word++ = ch; ch = getc(stdin); } /* end of while */ *word = '\0'; /* 原来的代码这里有问题 */ return i; } /* end of nextin */ /* ------------------------------------------------------------------ * initw -- initialize the dictionary to contain no words at all * ------------------------------------------------------------------ */ int initw(void) { nwords = 0; return 1; } /* end of initw */ /* ------------------------------------------------------------------ * insertw -- insert a word in the dictionary * ------------------------------------------------------------------ */ int insertw(const char *word) { strcpy(dict[nwords], word); nwords++; return (nwords); } /* end of insertw */ /* ------------------------------------------------------------------ * deletew -- delete a word from the dictionary * ------------------------------------------------------------------ */ int deletew(const char *word) { int i; for (i = 0; i < nwords; i++) { if (strcmp(word, dict[i]) == 0) { nwords--; strcpy(dict[i], dict[nwords]); return (1); } } /* end of for */ return (0); } /* end of deletew */ /* ------------------------------------------------------------------ * lookupw -- look up a word in the dictionary * ------------------------------------------------------------------ */ int lookupw(const char *word) { int i; for (i = 0; i < nwords; i++) { if (strcmp(word, dict[i]) == 0) { return (1); } } /* end of for */ return (0); } /* end of lookupw */ |
这是一个简单的字典程序,即程序运行起来以后维护着一个字典库,用户可以向里面添加词语,也可以查询或删除词语。
当然,这个程序只能在同一台主机上运行。程序整个运行过程中,只需要完成如下几个步骤:
A、接受用户输入;
B、分析用户输入决定是否进行下面的步骤:
1、初始化数据库;
2、向数据库添加词语;
3、查询或删除词语
任务分解
大家可以想到,对于一个大型系统,比如需要有很多人维护这个系统的数据。象上面这样独立的程序就不适用了,需要做成分布式系统:
即一个服务器维护着数据库,任何客户端都可以接受用户请求,客户端分析用户命令后提交给服务器去处理。
所以我们可能会把程序分成两部分:
客户端:接受用户输入,并判断用户输入内容的正确性,向服务器提交数据,等服务器返回消息
服务器端:维护数据,接受客户端命令并执行后返回结果。
所以我们把上面这个程序分解成下面两部分:
/* dict1.c -- main, nextin */ #include #include #define MAXWORD 50 /* maximum length of a command or word */ /* ------------------------------------------------------------------ * main -- insert, delete, or lookup words in a dictionary as specified * ------------------------------------------------------------------ */ int main(int argc, char *argv[]) { char word[MAXWORD + 1]; /* space to hold word from input line */ char cmd; int wordlen; /* length of input word */ printf("Please input:\n"); while (1) { wordlen = nextin(&cmd, word); if (wordlen < 0) { exit(0); } switch (cmd) { case 'I': /* 初始化 */ initw(); printf("Dictionary initialized to empty.\n"); break; case 'i': /* 插入 */ insertw(word); printf("%s inserted.\n", word); break; case 'd': /* 删除 */ if (deletew(word)) { printf("%s deleted.\n", word); } else { printf("%s not found.\n", word); } break; case 'l': /* 查询 */ if (lookupw(word)) { printf("%s was found.\n", word); } else { printf("%s was not found.\n", word); } break; case 'q': /* 退出 */ printf("Program quits.\n"); exit(0); break; default: /* 非法输入 */ printf("command %c invalid.\n", cmd); break; } /* end of switch */ } /* end of while */ return 0; } /* end of main */ /* ------------------------------------------------------------------ * nextin -- read a command and(possibly) a word from the next input line * ------------------------------------------------------------------ */ int nextin(char *cmd, char *word) { int i, ch; ch = getc(stdin); while (isspace(ch)) { ch = getc(stdin); } /* end of while */ if (ch == EOF) { return (-1); } *cmd = (char) ch; ch = getc(stdin); while (isspace(ch)) { ch = getc(stdin); } /* end of while */ if (ch == EOF) { return (-1); } if (ch == '\n') { return (0); } i = 0; while (!isspace(ch)) { if (++i > MAXWORD) { printf("error: word too long.\n"); exit(1); } *word++ = ch; ch = getc(stdin); } /* end of while */ *word = '\0'; return i; } /* end of nextin */ |
和
/* dict2.c -- initw, insertw, deletew, lookupw */ #include #define MAXWORD 50 /* maximum length of a command or word */ #define DICTSIZ 100 /* maximum number of entries in dictionary. */ char dict[DICTSIZ][MAXWORD + 1]; /* storage for a dictionary of words */ int nwords = 0; /* number of words in the dictionary */ /* ------------------------------------------------------------------ * initw -- initialize the dictionary to contain no words at all * ------------------------------------------------------------------ */ int initw(void) { nwords = 0; return 1; } /* end of initw */ /* ------------------------------------------------------------------ * insertw -- insert a word in the dictionary * ------------------------------------------------------------------ */ int insertw(const char *word) { strcpy(dict[nwords], word); nwords++; return (nwords); } /* end of insertw */ /* ------------------------------------------------------------------ * deletew -- delete a word from the dictionary * ------------------------------------------------------------------ */ int deletew(const char *word) { int i; for (i = 0; i < nwords; i++) { if (strcmp(word, dict[i]) == 0) { nwords--; strcpy(dict[i], dict[nwords]); return (1); } } /* end of for */ return (0); } /* end of deletew */ /* ------------------------------------------------------------------ * lookupw -- look up a word in the dictionary * ------------------------------------------------------------------ */ int lookupw(const char *word) { int i; for (i = 0; i < nwords; i++) { if (strcmp(word, dict[i]) == 0) { return (1); } } /* end of for */ return (0); } /* end of lookupw */ |
这两部分代码只是在功能上实现了分离,显然实现通讯的部分还没有,下面我们利用RPC来快速实现通讯。
利用RPC实现分布式系统
首先,建立一个RPC源文件,源代码rdict.x如下:
/* rdict.x */ /* RPC declarations for dictionary program */ const MAXWORD = 10; /* maximum length of a command or word */ const DICTSIZ = 3; /* number of entries in dictionary */ struct example /* unused structure declared here to */ { int exfield1; /* illustrate how rpcgen builds XDR */ char exfield2; /* routines to convert structures */ }; /* ------------------------------------------------------------------ * RDICTPROG -- remote program that provides insert, delete, and lookup * ------------------------------------------------------------------ */ program RDICTPROG /* name of remote program ( not used ) */ { version RDICTVERS /* declaration of version ( see below ) */ { int INITW ( void ) = 1; /* first procedure in this program */ int INSERTW ( string ) = 2; /* second procedure in this program */ int DELETEW ( string ) = 3; /* third procedure in this program */ int LOOKUPW ( string ) = 4; /* fourth procedure in this program */ } = 1; /* definition of the program version */ } = 0x30090949; /* remote program number ( must be unique ) */ |
然后用下列命令产生服务器端函数rdict_srv_func.c:
rpcgen -Ss -o rdict_srv_func.c rdict.x |
然后用下列命令产生客户端程序rdict_client.c:
rpcgen -Sc -o rdict_client.c rdict.x |
/************关于本文档********************************************
*filename: 我是这样学习Linux下C语言编程的-利用RPC快速实现分布式系统
*purpose: 说明如何利用RPC快速进行客户端-服务器端C-S结构编程
*wrote by: zhoulifa([email protected]) 周立发(http://zhoulifa.bokee.com)
Linux爱好者 Linux知识传播者 SOHO族 开发者 最擅长C语言
*date time:2007-02-27 19:20
*Note: 任何人可以任意复制代码并运用这些文档,当然包括你的商业用途
* 但请遵循GPL
*Thanks to:
* Ubuntu 本程序在Ubuntu 6.10系统上测试完全正常
* Google.com 我通过google搜索并参考了RPC编程相关的许多文章
* 网络安全焦点(www.xfocus.net) 我主要借鉴了此文 http://www.xfocus.net/articles/200009/10.html
*Hope:希望越来越多的人贡献自己的力量,为科学技术发展出力
* 科技站在巨人的肩膀上进步更快!感谢有开源前辈的贡献!
*********************************************************************/
然后用下列命令产生Makefile:
rpcgen -Sm rdict.x > Makefile |
Makefile文件原内容如下:
# This is a template Makefile generated by rpcgen # Parameters CLIENT = rdict_client SERVER = rdict_server SOURCES_CLNT.c = SOURCES_CLNT.h = SOURCES_SVC.c = SOURCES_SVC.h = SOURCES.x = rdict.x TARGETS_SVC.c = rdict_svc.c rdict_xdr.c TARGETS_CLNT.c = rdict_clnt.c rdict_xdr.c TARGETS = rdict.h rdict_xdr.c rdict_clnt.c rdict_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) |
动手修改Makefile,修改后内容如下:
# This is a template Makefile generated by rpcgen # Parameters CLIENT = rdict_client SERVER = rdict_server SOURCES_CLNT.c = SOURCES_CLNT.h = SOURCES_SVC.c = SOURCES_SVC.h = SOURCES.x = rdict.x TARGETS_SVC.c = rdict_svc.c rdict_xdr.c rdict_srv_func.c TARGETS_CLNT.c = rdict_clnt.c rdict_xdr.c rdict_client.c TARGETS = rdict.h rdict_xdr.c rdict_clnt.c rdict_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) *~ |
修改客户端源代码rdict_client.c,把接受用户输入并分析用户输入内容的部分加到程序中来。修改后的代码为:
/* * 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 "rdict.h" /* ------------------------------------------------------------------ * nextin -- read a command and(possibly) a word from the next input line * ------------------------------------------------------------------ */ int nextin(char *cmd, char *word) { int i, ch; ch = getc(stdin); while (isspace(ch)) { ch = getc(stdin); } /* end of while */ if (ch == EOF) { return (-1); } *cmd = (char) ch; ch = getc(stdin); while (isspace(ch)) { ch = getc(stdin); } /* end of while */ if (ch == EOF) { return (-1); } if (ch == '\n') { return (0); } i = 0; while (!isspace(ch)) { if (++i > MAXWORD) { printf("error: word too long.\n"); exit(1); } *word++ = ch; ch = getc(stdin); } /* end of while */ *word = '\0'; return i; } /* end of nextin */ void rdictprog_1(char *host) { CLIENT *clnt; int *result_1; char *initw_1_arg; int *result_2; char *insertw_1_arg; int *result_3; char *deletew_1_arg; int *result_4; char *lookupw_1_arg; #ifndef DEBUG clnt = clnt_create(host, RDICTPROG, RDICTVERS, "udp"); if (clnt == NULL) { clnt_pcreateerror(host); exit(1); } #endif /* DEBUG */ char word[MAXWORD + 1]; /* space to hold word from input line */ char cmd; int wordlen; /* length of input word */ while (1) { printf("\nPlease input:"); wordlen = nextin(&cmd, word); if (wordlen < 0) { exit(0); } /* printf("\nYour cmd is:%c, your word is:%s\n", cmd, word); */ switch (cmd) { case 'I': /* 初始化 */ result_1 = initw_1((void *) &initw_1_arg, clnt); /* printf("\nYour result is:%d\n", *result_1); */ if (result_1 == (int *) NULL) clnt_perror(clnt, "call failed"); else if(*result_1 ==0) printf("Dictionary initialized to empty.\n"); else printf("Dictionary have already initialized.\n"); break; case 'i': /* 插入 */ insertw_1_arg = word; result_2 = insertw_1(&insertw_1_arg, clnt); /* printf("\nYour result is:%d, your string is:%s(%d)\n", *result_2, insertw_1_arg, strlen(insertw_1_arg)); */ if (result_2 == (int *) NULL) clnt_perror(clnt, "call failed"); else printf("%s inserted.\n", word); break; case 'd': /* 删除 */ deletew_1_arg = word; result_3 = deletew_1(&deletew_1_arg, clnt); /* printf("\nYour result is:%d, your string is:%s(%d)\n", *result_3, deletew_1_arg, strlen(deletew_1_arg)); */ if (result_3 == (int *) NULL) clnt_perror(clnt, "call failed"); else printf("%s deleted.\n", word); break; case 'l': /* 查询 */ lookupw_1_arg = word; result_4 = lookupw_1(&lookupw_1_arg, clnt); /* printf("\nYour result is:%d, your string is:%s(%d)\n", *result_4, lookupw_1_arg, strlen(lookupw_1_arg)); */ if (result_4 == (int *) NULL) clnt_perror(clnt, "call failed"); else if(*result_4 ==0) printf("%s found.\n", word); else printf("%s not found.\n", word); break; case 'q': /* 退出 */ printf("Program quits.\n"); exit(0); break; default: /* 非法输入 */ printf("Command %c(%s) invalid.\n", cmd, word); break; } /* end of switch */ } /* end of while */ #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]; rdictprog_1(host); exit(0); } |
同时修改服务器端代码rdict_srv_func.c,修改后内容为:
/* * 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 "rdict.h" char dict[DICTSIZ][MAXWORD + 1]; /* storage for a dictionary of words */ int nwords = 0; /* number of words in the dictionary */ char init_bool = 0; int initw(void) { if(init_bool) return 1; nwords = 0; init_bool = 1; return 0; } /* end of initw */ /* ------------------------------------------------------------------ * insertw -- insert a word in the dictionary * ------------------------------------------------------------------ */ int insertw(const char *word) { strcpy(dict[nwords%DICTSIZ], word); nwords++; return (nwords); } /* end of insertw */ /* ------------------------------------------------------------------ * deletew -- delete a word from the dictionary * ------------------------------------------------------------------ */ int deletew(const char *word) { int i; for (i = 0; i < nwords; i++) { if (strcmp(word, dict[i]) == 0) { nwords--; strcpy(dict[i], dict[nwords]); return (1); } } /* end of for */ return (0); } /* end of deletew */ /* ------------------------------------------------------------------ * lookupw -- look up a word in the dictionary * ------------------------------------------------------------------ */ int lookupw(const char *word) { int i; for (i = 0; i < nwords; i++) { if (strcmp(word, dict[i]) == 0) { return 0; } } /* end of for */ return 1; } /* end of lookupw */ int *initw_1_svc(void *argp, struct svc_req *rqstp) { static int result; /* * insert server code here */ result = initw(); return &result; } int *insertw_1_svc(char **argp, struct svc_req *rqstp) { static int result; /* * insert server code here */ result = insertw(*argp); return &result; } int *deletew_1_svc(char **argp, struct svc_req *rqstp) { static int result; /* * insert server code here */ result = deletew(*argp); return &result; } int *lookupw_1_svc(char **argp, struct svc_req *rqstp) { static int result; /* * insert server code here */ result = lookupw(*argp); return &result; } |
至此,程序做好了。输入一个make命令就可以生成test_server和test_client这两个可执行程序了。
在一台机器上运行./test_server程序,在另外的客户机上运行./test_client server_ip就可以了。这里server_ip是运行着test_server程序的主机的IP地址。