net::ERR_INCOMPLETE_CHUNKED_ENCODING 200 (OK) - c

Question

I am new in networking and I try to write my first http server on C. However i faced a problem. When i try to send image by chunks i recive an error GET http://localhost/img.jpg net::ERR_INCOMPLETE_CHUNKED_ENCODING 200 (OK), whith html it works fine.
void answerOnGet(int socketCopy, char *fileName)
{
struct stat sbuf;
char filePath[SIZE];
determinateFilePath(fileName, filePath);
stat(filePath, &sbuf);
char responseHeader[2*SIZE];
char fileType[SIZE];
if (strstr(fileName, ".html") || !strcmp(fileName, "/"))
{
strcpy(fileType, "text/html");
}
else if (strstr(fileName, ".jpg"))
{
strcpy(fileType, "image/jpg");
}
else if(strstr(fileName, ".ico"))
{
strcpy(fileType, "image/ico");
}
else
{
fprintf(stderr, "Type error\n");
exit(1);
}
FILE *fd = fopen(filePath, "rb");
if(fd == NULL)
{
perror("Opening error");
exit(1);
}
snprintf(responseHeader, sizeof(responseHeader),
"HTTP/1.1 200 OK\r\n"
"Transfer-Encoding: chunked\r\n"
"Content-type: %s\r\n\r\n", fileType
);
if(write(socketCopy, responseHeader, strlen(responseHeader)) < 0)
{
perror("Write error");
exit(1);
}
long unsigned sizeOfChunk = 0;
if(sbuf.st_size > SIZE)
{
sizeOfChunk = sbuf.st_size/50;
}
else
{
sizeOfChunk = sbuf.st_size;
}
char *buf = malloc(sizeof(char) * (sizeOfChunk + 2));
printf("Size of chunk = %ld\n", sizeOfChunk);
char amountOfBytes[SIZE];
while(fread(buf, sizeof(char), sizeOfChunk, fd) == (sizeOfChunk))
{
sprintf(amountOfBytes, "%lX\r\n", sizeOfChunk);
puts("\nStart to write");
if(write(socketCopy, amountOfBytes, strlen(amountOfBytes)) < 0)
{
perror("Write bytes error");
exit(1);
}
strcat(buf, "\r\n");
if(write(socketCopy, buf, strlen(buf)) < 0)
{
perror("Write error");
exit(1);
}
puts("\nEnd of write");
bzero(buf, sizeOfChunk);
bzero(amountOfBytes, strlen(amountOfBytes));
}
puts("Send zero chunk");
if(write(socketCopy, "0\r\n\r\n", strlen("0\r\n\r\n")) < 0)
{
perror("Write zero chunk error");
exit(1);
}
fclose(fd);
free(buf);
}

Answer 1

Your mistake is most likely
if(write(socketCopy, buf, strlen(buf)) < 0)
What does strlen(buf) do? It counts the number of bytes up to the first 0 byte.
Is that the correct number of bytes to write? Only if there's a 0 byte at the end and none before that.
Is there? Well, no. Files can have 0 bytes in the middle and fread does not put one at the end.
Instead of strlen(buf) you should use sizeOfChunk.
Other bugs:
As #rveerd pointed out, it's possible that you call write and the kernel only writes part of the data. If that happens, you still have to call it again to write the rest of the data. This may happen multiple times so you need a loop. I suggest making a function actually_write which does the loop, then you can call actually_write(socketCopy, buf, sizeOfChunk)
Your program doesn't send some of the bytes at the end sometimes. If the file is, for example, 1001 bytes long, then you do 20-byte chunks, and after the last full chunk there is still one byte, and fread returns 1 but you don't send the extra byte.