用c实现http协议 - vfdff的博客

作者在 2008-10-31 21:22:09 发布以下内容

大家都很熟悉HTTP协议的应用，因为每天都在网络上浏览着不少东西，也都知道是HTTP协议是相当简单的。每次用thunder之类的下载软件下载网页，当用到那个“用thunder下载全部链接”时总觉得很神奇。后来想想，其实要实现这些下载功能也并不难，只要按照HTTP协议发送request，然后对接收到的数据进行分析，如果页面上还有href之类的链接指向标志就可以进行深一层的下载了。HTTP协议目前用的最多的是1.1版本，要全面透彻地搞懂它就参考RFC2616文档吧。我是怕rfc文档了的,要看自己去看吧^_^ 源代码如下： /******* http客户端程序 httpclient.c ************/ #include <stdio.h> #include <stdlib.h> #include <string.h> #include <sys/types.h> #include <sys/socket.h> #include <errno.h> #include <unistd.h> #include <netinet/in.h> #include <limits.h> #include <netdb.h> #include <arpa/inet.h> #include <ctype.h> //////////////////////////////httpclient.c 开始/////////////////////////////////////////// /******************************************** 功能：搜索字符串右边起的第一个匹配字符 ********************************************/ char * Rstrchr(char * s, char x) { int i = strlen(s); if(!(*s)) return 0; while(s[i-1]) if(strchr(s + (i - 1), x)) return (s + (i - 1)); else i--; return 0; } /******************************************** 功能：把字符串转换为全小写 ********************************************/ void ToLowerCase(char * s) { while(s && *s) {*s=tolower(*s);s++;} } /************************************************************** 功能：从字符串src中分析出网站地址和端口，并得到用户要下载的文件 ***************************************************************/ void GetHost(char * src, char * web, char * file, int * port) { char * pA; char * pB; memset(web, 0, sizeof(web)); memset(file, 0, sizeof(file)); *port = 0; if(!(*src)) return; pA = src; if(!strncmp(pA, "http://", strlen("http://"))) pA = src+strlen("http://"); else if(!strncmp(pA, "https://", strlen("https://"))) pA = src+strlen("https://"); pB = strchr(pA, '/'); if(pB) { memcpy(web, pA, strlen(pA) - strlen(pB)); if(pB+1) { memcpy(file, pB + 1, strlen(pB) - 1); file[strlen(pB) - 1] = 0; } } else memcpy(web, pA, strlen(pA)); if(pB) web[strlen(pA) - strlen(pB)] = 0; else web[strlen(pA)] = 0; pA = strchr(web, ':'); if(pA) *port = atoi(pA + 1); else *port = 80; } int main(int argc, char *argv[]) { int sockfd; char buffer[1024]; struct sockaddr_in server_addr; struct hostent *host; int portnumber,nbytes; char host_addr[256]; char host_file[1024]; char local_file[256]; FILE * fp; char request[1024]; int send, totalsend; int i; char * pt; if(argc!=2) { fprintf(stderr,"Usage:%s web-address\a\n",argv[0]); exit(1); } printf("parameter.1 is: %s\n", argv[1]); ToLowerCase(argv[1]);/*将参数转换为全小写*/ printf("lowercase parameter.1 is: %s\n", argv[1]); GetHost(argv[1], host_addr, host_file, &portnumber);/*分析网址、端口、文件名等*/ printf("webhost:%s\n", host_addr); printf("hostfile:%s\n", host_file); printf("portnumber:%d\n\n", portnumber); if((host=gethostbyname(host_addr))==NULL)/*取得主机IP地址*/ { fprintf(stderr,"Gethostname error, %s\n", strerror(errno)); exit(1); } /* 客户程序开始建立 sockfd描述符 */ if((sockfd=socket(AF_INET,SOCK_STREAM,0))==-1)/*建立SOCKET连接*/ { fprintf(stderr,"Socket Error:%s\a\n",strerror(errno)); exit(1); } /* 客户程序填充服务端的资料 */ bzero(&server_addr,sizeof(server_addr)); server_addr.sin_family=AF_INET; server_addr.sin_port=htons(portnumber); server_addr.sin_addr=*((struct in_addr *)host->h_addr); /* 客户程序发起连接请求 */ if(connect(sockfd,(struct sockaddr *)(&server_addr),sizeof(struct sockaddr))==-1)/*连接网站*/ { fprintf(stderr,"Connect Error:%s\a\n",strerror(errno)); exit(1); } sprintf(request, "GET /%s HTTP/1.1\r\nAccept: */*\r\nAccept-Language: zh-cn\r\n\ User-Agent: Mozilla/4.0 (compatible; MSIE 5.01; Windows NT 5.0)\r\n\ Host: %s:%d\r\nConnection: Close\r\n\r\n", host_file, host_addr, portnumber); printf("%s", request);/*准备request，将要发送给主机*/ /*取得真实的文件名*/ if(host_file && *host_file) pt = Rstrchr(host_file, '/'); else pt = 0; memset(local_file, 0, sizeof(local_file)); if(pt && *pt) { if((pt + 1) && *(pt+1)) strcpy(local_file, pt + 1); else memcpy(local_file, host_file, strlen(host_file) - 1); } else if(host_file && *host_file) strcpy(local_file, host_file); else strcpy(local_file, "index.html"); printf("local filename to write:%s\n\n", local_file); /*发送http请求request*/ send = 0;totalsend = 0; nbytes=strlen(request); while(totalsend < nbytes) { send = write(sockfd, request + totalsend, nbytes - totalsend); if(send==-1) {printf("send error!%s\n", strerror(errno));exit(0);} totalsend+=send; printf("%d bytes send OK!\n", totalsend); } fp = fopen(local_file, "a"); if(!fp) { printf("create file error! %s\n", strerror(errno)); return 0; } printf("\nThe following is the response header:\n"); i=0; /* 连接成功了，接收http响应，response */ while((nbytes=read(sockfd,buffer,1))==1) { if(i < 4) { if(buffer[0] == '\r' || buffer[0] == '\n') i++; else i = 0; printf("%c", buffer[0]);/*把http头信息打印在屏幕上*/ } else { fwrite(buffer, 1, 1, fp);/*将http主体信息写入文件*/ i++; if(i%1024 == 0) fflush(fp);/*每1K时存盘一次*/ } } fclose(fp); /* 结束通讯 */ close(sockfd); exit(0); }

zj@zj:~/C_pram/practice/http_client$ ls httpclient httpclient.c zj@zj:~/C_pram/practice/http_client$ ./httpclient http://www.baidu.com/ parameter.1 is: http://www.baidu.com/ lowercase parameter.1 is: http://www.baidu.com/ webhost:www.baidu.com hostfile: portnumber:80 GET / HTTP/1.1 Accept: */* Accept-Language: zh-cn User-Agent: Mozilla/4.0 (compatible; MSIE 5.01; Windows NT 5.0) Host: www.baidu.com:80 Connection: Close local filename to write:index.html 163 bytes send OK! The following is the response header: HTTP/1.1 200 OK Date: Wed, 29 Oct 2008 10:41:40 GMT Server: BWS/1.0 Content-Length: 4216 Content-Type: text/html Cache-Control: private Expires: Wed, 29 Oct 2008 10:41:40 GMT Set-Cookie: BAIDUID=A93059C8DDF7F1BC47C10CAF9779030E:FG=1; expires=Wed, 29-Oct-38 10:41:40 GMT; path=/; domain=.baidu.com P3P: CP=" OTI DSP COR IVA OUR IND COM " zj@zj:~/C_pram/practice/http_client$ ls httpclient httpclient.c index.html

不指定文件名字的话,默认就是下载网站默认的首页了^_^.