在c中通过套接字发送图像文件的问题 [英] problem sending image file over the socket in c
问题描述
我正在编写一个支持 HTTP 的基于 C 的服务器.&buffer[5] 具有文件名.我在下一步设置标题，然后以 8Kb 的块发送文件.当我请求一个 txt 文件时它工作正常，但是当我请求一个 jpg 文件时，它没有提供任何 o/p.我需要对图像文件采取什么特别的措施还是有其他问题.
I am writing a C based server supporting HTTP. &buffer[5] has the file name. I set the header in next step and then send the file in block of 8Kb. It is working fine when I am requesting a txt file, but when I request a jpg file, it is not giving any o/p. Is there any specific care I need to take for image file or there is some other problem.
void web(int fd)
{
int j, file_fd;
int buflen; int len;
long i, ret;
char * fstr;
static char buffer[BUFSIZE+1]; /* static so zero filled */
ret =read(fd,buffer,BUFSIZE); /* read Web request in one go */
if(ret == 0 || ret == -1) { /* read failure stop now */
//log1(SORRY,"failed to read browser request","",fd);
}
if(ret > 0 && ret < BUFSIZE) /* return code is valid chars */
buffer[ret]=0; /* terminate the buffer */
else buffer[0]=0;
for(i=0;i<ret;i++) /* remove CF and LF characters */
if(buffer[i] == '
' || buffer[i] == '
')
buffer[i]='*';
log1(LOG,"request",buffer,1);
if( strncmp(buffer,"GET ",4) && strncmp(buffer,"get ",4) )
log1(SORRY,"Only simple GET operation supported",buffer,fd);
for(i=4;i<BUFSIZE;i++) { /* null terminate after the second space to ignore extra stuff */
if(buffer[i] == ' ') { /* string is "GET URL " +lots of other stuff */
buffer[i] = 0;
break;
}
}
for(j=0;j<i-1;j++) /* check for illegal parent directory use .. */
if(buffer[j] == '.' && buffer[j+1] == '.')
log1(SORRY,"HTTP/1.0 400 Bad Request: Invalid URI:
Parent directory (..) path names not supported",buffer,fd);
if( !strncmp(&buffer[0],"GET / ",6) || !strncmp(&buffer[0],"get / ",6) ) /* convert no filename to index file */
(void)strcpy(buffer,"GET /index.html");
/* work out the file type and check we support it */
buflen=strlen(buffer);
fstr = (char *)0;
for(i=0;extensions[i].ext != 0;i++) {
len = strlen(extensions[i].ext);
printf("%s %s %d
", &buffer[buflen-len],extensions[i].ext, strncmp(&buffer[buflen-len], extensions[i].ext, len));
if( !strncmp(&buffer[buflen-len], extensions[i].ext, len)) {
fstr =extensions[i].filetype;
break;
}
}
if(fstr == 0)
log1(SORRY,"HTTP/1.0 400 Bad Request: Invalid URI:
file extension type not supported",buffer,fd);
printf("Buffer Value: %s
",&buffer[5]);
if(( file_fd = open(&buffer[5],O_RDONLY)) == -1) /* open the file for reading */
{
log1(SORRY, "HTTP/1.0 404 Not Found
failed to open file",&buffer[5],fd);}
printf("file Descrptr:%d
",file_fd);
log1(LOG,"SEND",&buffer[5],1);
(void)sprintf(buffer,"HTTP/1.0 200 OK
Content-Type: %s
", fstr);
(void)write(fd,buffer,strlen(buffer));
printf("Buffer Header:%s
",buffer);
//int rec = read(file_fd, buffer, 10*BUFSIZE);
/* send file in 8KB block - last block may be smaller */
while ( (ret = read(file_fd, buffer, BUFSIZE)) > 0 ) {
(void)write(fd,buffer,ret);
printf("BufferData:%d
",strlen(buffer));
}
#ifdef LINUX
sleep(1); /* to allow socket to drain */
#endif
exit(1);
}
o/p 用于 jpg 文件:
o/p for jpg file:
server: got connection from 127.0.0.1
Buffer Header:HTTP/1.0 200 OK
Content-Type: image/jpeg
BufferData:4
BufferData:95
BufferData:122
BufferData:24
BufferData:217
对于txt文件:
Buffer Value: config.txt
file Descrptr:4
Buffer Header:HTTP/1.0 200 OK
Content-Type: text/plain
BufferData:416
推荐答案
如果您的代码适用于 txt 文件，请尝试使用 fread/fwrite 而不是 read/write .txt 文件中不存在的 jpg 图像中的 NULL 字符可能存在问题.并且在标题中包含内容长度，否则在某些情况下，即使您的下载完成，您的浏览器也会继续请求.简而言之，浏览器不知道何时停止.
If your code is working for txt files, give fread/fwrite a try instead of read/write . There might be a problem with NULL characters in jpg image which are not present in txt files. And do include a content length in header otherwise in some cases your browser will keep on requesting even if your download has finished. In simple words browser don't know when to stop.
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