send a file without waiting the reception of the whole file - c

Question

I have a Server that contact another Server in order to obtain a file and then send it to the Client. I have write this piece of code (C - Linux) but only the first 4 bytes arrive to the Client.
Someone better than me can see the mistake?
Thank you very much
int Recv_file (int s, int f, char *ptr, size_t maxlen){
int const TIMEOUT = 60; /* 60 seconds */
size_t n;
ssize_t nread;
ssize_t nsend;
char c;
fd_set cset;
struct timeval tval;
int x;
for (n=1; n<maxlen; n++)
{
FD_ZERO(&cset);
FD_SET(s, &cset);
tval.tv_sec = TIMEOUT;
tval.tv_usec = 0;
x = select(FD_SETSIZE, &cset, NULL, NULL, &tval);
if (x==-1) {
perror("select() failed");
return -1; /* -1 = close connection with the client */
}
if (x>0) {
nread=recv(s, &c, 1, 0);
if (nread == 1)
{
*ptr++ = c;
nsend = Send(f,&c,1);
if (nsend != 1) {
return -1; /* close connection with the client */
}
}else if (nread == 0){
*ptr = 0;
return (-1); /* close connection with the client */
}
else
return (-1); /* close connection with the client */
}else{
printf("(It's been %d seconds and I have not received any response",TIMEOUT);
close(s);
return(-1); /* close connection with the client */
}
}
*ptr = 0;
return (n); /* n == maxlen */
}
with:
int Send(int s, char *ptr, size_t nbytes){
size_t nleft;
ssize_t nwritten;
for (nleft=nbytes; nleft > 0; )
{
nwritten = send(s, ptr, nleft, 0);
if (nwritten <=0)
return (nwritten);
else
{
nleft -= nwritten;
ptr += nwritten;
}
}
return (nbytes - nleft); /* number of bytes sent */
}
UPDATE:
While waiting for an answer I modified:
nread=recv(s, &c, 1, 0); in nread=recv(s, &c, sizeof(c), 0);
and
Send(f,&c,1); in Send(f,&c,sizeof(c));
But now I don't receive the last bytes of the file!
Thank you again!

Answer 1

You don't get the last byte because the for loop start at 1
for (n=1; n<maxlen; n++);
// it should be
for (n=0; n<maxlen; n++);
// or either
for (n=1; n<=maxlen; n++);
EDIT: Also, you could read as much bytes as are available not just one by one, in fact you are sending in the correct way,
For example:
int bLeft = maxlen;
while (bLeft > 0)
{
FD_ZERO(&cset);
FD_SET(s, &cset);
tval.tv_sec = TIMEOUT;
tval.tv_usec = 0;
x = select(FD_SETSIZE, &cset, NULL, NULL, &tval);
if (x > 0) {
nread=recv(s, ptr, bLeft , 0);
if (nread > 0)
{
nsend = Send(f, ptr, nread, 0);
if (nsend <= 0) {
return -1; /* close connection with the client */
}
ptr+ = nread;
bLeft -= nread;
}else if (nread == 0){
*ptr = 0;
return (-1); /* close connection with the client */
}
else
return (-1); /* close connection with the client */
}else{
printf("(It's been %d seconds and I have not received any response",TIMEOUT);
close(s);
return(-1); /* close connection with the client */
}
}
// I would not recommended this, you should adhere to a maxlen length
// assuming there is more space could lead to a memory Exception.
ptr++;
*ptr ='\0';
return (maxlen-bLeft);