Sending Picture via TCP - c++

Question

I'm trying to send a jpg file from a client to a server using TCP. When the picture arrives to the server side I can't open it, besides the size of the picture received is higher than the one sent (sent = 880 bytes , received = 894 bytes). Any one of you have an idea of how to do solve this problem ? Here is my code :
client code :
static int send_server_image(SOCKET sock){
int n = 0;
int siz = 0;
FILE *picture;
char buf[50];
char *s="";
cout << "Getting image size" << endl;
picture = fopen("C:\\Users\\n.b\\Desktop\\c++\\TCP\\tcp_client_image_pp\\test.jpg", "r");
fseek(picture, 0, SEEK_END);
siz = ftell(picture);
cout << siz << endl; // Output 880
cout << "Sending picture size to the server" << endl;
sprintf(buf, "%d", siz);
if((n = send(sock, buf, sizeof(buf), 0)) < 0)
{
perror("send_size()");
exit(errno);
}
char Sbuf[siz];
cout << "Sending the picture as byte array" << endl;
fseek(picture, 0, SEEK_END);
siz = ftell(picture);
fseek(picture, 0, SEEK_SET); //Going to the beginning of the file
while(!feof(picture)){
fread(Sbuf, sizeof(char), sizeof(Sbuf), picture);
if((n = send(sock, Sbuf, sizeof(Sbuf), 0)) < 0)
{
perror("send_size()");
exit(errno);
}
memset(Sbuf, 0, sizeof(Sbuf));
}
}
server code :
static int recv_client_image(SOCKET sock){
int n = 0;
cout << "Reading image size" << endl;
char buf[50];
int siz = 0;
if ((n = recv(sock, buf, sizeof(buf), 0) <0)){
perror("recv_size()");
exit(errno);
}
siz = atoi(buf);
cout << siz << endl; // 880 output
char Rbuffer[siz];
cout << "Reading image byte array" << endl;
n = 0;
if ((n = recv(sock, Rbuffer, sizeof(Rbuffer), 0)) < 0){
perror("recv_size()");
exit(errno);
}
cout << "Converting byte array to image" << endl;
FILE *image;
image = fopen("recu.jpg", "w");
fwrite(Rbuffer, sizeof(char), sizeof(Rbuffer), image);
fclose(image);
cout << "done" << endl;
}
Thank you.

Answer 1

You are using Variable Length Arrays, which is not standard C++ (ref). Even if it is accepted by your compiler, you should avoid using sizeof on that.
And you have a problem in the while(!feof(picture)). You read siz bytes from the file without any error and without setting the eof flag. On second read, you read 0 bytes and set the flag but also send another buffer.
You should write instead:
while(!feof(picture)){
n = fread(Sbuf, sizeof(char), siz, picture);
if (n > 0) { /* only send what has been read */
if((n = send(sock, Sbuf, siz, 0)) < 0) /* or (better?) send(sock, Sbuf, n, 0) */
{
perror("send_data()");
exit(errno);
}
}
/* memset(Sbuf, 0, sizeof(Sbuf)); useless for binary data */
}
Same in server part:
if ((n = recv(sock, Rbuffer, siz, 0)) < 0){
perror("recv_size()");
exit(errno);
}
cout << "Converting byte array to image" << endl;
FILE *image;
image = fopen("recu.jpg", "w");
fwrite(Rbuffer, sizeof(char), siz, image);
fclose(image);
And there is a last possibility of error, at least if you are on a platform that makes a difference between text and binary file like Windows is that you forget to open the files in binary mode, which could break the jpg image. Because on windows for a binary file, byte 0x10 is seen as the new line (\n') and written as 2 bytes 0x0d 0x10 (\r\n).
So you must open the input file in rb mode and the output file in wb mode.

Answer 2

Solved :
All the correction that Serge Ballesta were right. But the problem was in the way I was opening my files.
You need to open the file in binary mode ("rb" for reading, "wb" for writing), not the default text mode.
Client :
picture = fopen("C:\\Users\\n.b\\Desktop\\c++\\TCP\\tcp_client_image_pp\\test.jpg", "rb");
Server :
image = fopen("recu.jpg", "wb");
That was the main problem. Thank you.