#include <sys/socket.h>

#include <netinet/in.h>

#include <arpa/inet.h>

#include <signal.h>

#include <errno.h>

#include <unistd.h>

#include <stdlib.h>

#include <assert.h>

#include <stdio.h>

#include <string.h>

#include <sys/stat.h>

#include <sys/types.h>

#include <fcntl.h>

#define BUFFER_SIZE 1024

static const char* status_line[2] = {"200 OK","500 Internal sesrver error"};

int main( int argc, char* argv[] )

{

if( argc <= 3)

{

printf("usage:%s ip_address port_number\n", basename(argv[0]) );

return 1;

}

const char* ip = argv[1];

int port = atoi( argv[2] );

//将目标文件作为程序的第三个参数传入

const char* file_name = argv[3];

struct sockaddr_in address;

bzero( &address, sizeof( address ) );

address.sin_family = AF_INET;

inet_pton( AF_INET, ip, &address.sin_addr );

address.sin_port = htons( port );

int sock = socket( PF_INET, SOCK_STREAM, 0);

assert( sock >= 0 );

int ret = bind(sock,(struct sockaddr*)&address, sizeof(address));

assert( ret != 1 );

ret = listen(sock,5);

assert( ret != 1 );

struct sockaddr_in client;

socklen_t client_addrlength = sizeof( client );

int connfd = accept( sock, (struct sockaddr*)&client, &client_addrlength);

if( connfd < 0 )

{

printf("errno is:%d\n",errno);

}

else

{

//用于保存HTTP应答的状态行、头部字段和一个空行的缓存区

char header_buf[ BUFFER_SIZE ];

memset( header_buf, '\0', BUFFER_SIZE);

//用于存放目标文件内容的应用程序缓存

char* file_buf;

//用户获取目标文件的属性。比如是否目录，文件大小等

struct stat file_stat;

//记录目标文件是否有效文件

bool valid = true;

//缓存区header_buf目前已经使用了多少字节的空间

int len = 0;

if( stat( file_name, &file_stat) < 0 )//目标文件不存在

{

valid = false;

}

else

{

if(S_ISDIR( file_stat.st_mode ) ) //目标文件是一个目录

{

valid = false;

}

else if (file_stat.st_mode & S_IROTH) //当前用户有读取目标文件的权限

{

/*动态分配缓存区file_buf,并指定其大小为目标文件的大小file_stat.st_size加1，

然后将目标文件读入缓存区file_buf中*/

int fd = open(file_name,O_RDONLY);

file_buf = new char[file_stat.st_size+1];

memset( file_buf, '\0', file_stat.st_size + 1);

if( read( fd, file_buf, file_stat.st_size ) < 0 )

{

valid = false;

}

}

else

{

valid = false;

}

}

if( valid )

{

//将HTTP应答的状态行、"Content-Length" 头部字段和一个空行依次加入header_buf中

ret = snprintf( header_buf, BUFFER_SIZE-1, "%s %s\r\n","HTTP/1.1", status_line[0]);

len += ret;

ret = snprintf(header_buf + len, BUFFER_SIZE-1-len, "Content-Length: %d\r\n", file_stat.st_size);

len += ret;

ret = snprintf(header_buf + len, BUFFER_SIZE-1-len, "%s", "\r\n");

//利用writev将header_buf和file_buf的内容一并写出

struct iovec iv[2];

iv[ 0 ].iov_base = header_buf;

iv[ 0 ].iov_len = strlen(header_buf);

iv[ 1 ].iov_base = file_buf;

iv[ 1 ].iov_len = strlen(file_buf);

ret = writev(connfd, iv, 2);

}

else //如果目标文件无效，则通知客户端服务器发生了“内部错误”

{

ret = snprintf( header_buf, BUFFER_SIZE-1, "%s %s\r\n","HTTP/1.1", status_line[1]);

len += ret;

ret = snprintf(header_buf + len, BUFFER_SIZE-1-len, "%s", "\r\n");

send(connfd, header_buf, strlen(header_buf), 0 );

}

close( connfd );

delete [] file_buf;

}

close( sock );

return 0;

}