http下载网页

//http.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>

/********************************************
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=tolower(*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;
}

/*********************************************************************
*filename: http.c
*purpose: HTTP协议客户端程序，可以用来下载网页 下载http服务器的文件
*********************************************************************/
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);
}

//******************************************//

linux下编译

命令:

gcc http.c -o http

ls

./http http://baidu.com/test.html

显示：

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: Thu, 16 Nov 2017 03:23:19 GMT
Content-Type: text/html; charset=utf-8
Transfer-Encoding: chunked
Connection: Close
Vary: Accept-Encoding
Set-Cookie: BAIDUID=A8834922B6D30BB2F14E43B4EF6494FF:FG=1; expires=Thu, 31-Dec-37 23:55:55 GMT; max-age=2147483647; path=/; domain=.baidu.com
Set-Cookie: BIDUPSID=A8834922B6D30BB2F14E43B4EF6494FF; expires=Thu, 31-Dec-37 23:55:55 GMT; max-age=2147483647; path=/; domain=.baidu.com
Set-Cookie: PSTM=1510802599; expires=Thu, 31-Dec-37 23:55:55 GMT; max-age=2147483647; path=/; domain=.baidu.com
Set-Cookie: BDSVRTM=0; path=/
Set-Cookie: BD_HOME=0; path=/
Set-Cookie: H_PS_PSSID=1430_24868_13290_21110_24879; path=/; domain=.baidu.com
P3P: CP=" OTI DSP COR IVA OUR IND COM "
Cache-Control: private
Cxy_all: baidu+9252c7ff064baeb146003978af4dad38
Expires: Thu, 16 Nov 2017 03:22:59 GMT
X-Powered-By: HPHP
Server: BWS/1.1
X-UA-Compatible: IE=Edge,chrome=1
BDPAGETYPE: 1
BDQID: 0xd0d6dd0d0000eec0
BDUSERID: 0

不指定文件名字的话,默认就是下载网站默认的首页了