Socket Receive Binary

[iwasinnihon]

I am writing a simple program to receive over http using windows
sockets. my program does fine receiving text files. But returns the
incorrect data when receiving image files. (The size of the files are
different). My code is below. The header has already been read using
the same Receive() function. What have I done wrong.

ofstream os("file.dat", ios::binary);

//Retrieve the body
try {
while (1) {
l = s.Receive();
if (l.empty()) break;

os.write(l.c_str(), l.length());

//cout << l;
//length += l.length();
//cout.flush();
}
}
catch (const char* s) {
cerr << s << endl;
}
catch (string s) {
cerr << s << endl;
}
catch (...) {
cerr << "unhandled exception\n";
}
os.close();

string Socket::Receive() {
string ret;
while (1) {
char r;

switch(recv(sock, &r, 1, 0)) {
case 0:
return "";
case -1:
if (errno == EAGAIN)
return ret;
else
return "";
}

ret += r;
if (r == '\n') return ret;
}
}

[Andre Kostur]

"iwasinnihon" <iw*********@hotmail.comwrote in
news:11**********************@a34g2000cwb.googlegr oups.com:

I am writing a simple program to receive over http using windows
sockets. my program does fine receiving text files. But returns the
incorrect data when receiving image files. (The size of the files are
different). My code is below. The header has already been read using
the same Receive() function. What have I done wrong.

Out of curiosity.. have you tried this code with a text file that doesn't
end in a newline? (Hint: I suspect you have a problem when recv returns a
0.... what happens to all of the data that you have accumulated since the
last newline?)

ofstream os("file.dat", ios::binary);

//Retrieve the body
try {
while (1) {
l = s.Receive();
if (l.empty()) break;

os.write(l.c_str(), l.length());

//cout << l;
//length += l.length();
//cout.flush();
}
}
catch (const char* s) {
cerr << s << endl;
}
catch (string s) {
cerr << s << endl;
}
catch (...) {
cerr << "unhandled exception\n";
}
os.close();

string Socket::Receive() {
string ret;
while (1) {
char r;

switch(recv(sock, &r, 1, 0)) {
case 0:
return "";
case -1:
if (errno == EAGAIN)
return ret;
else
return "";
}

ret += r;
if (r == '\n') return ret;
}
}

[Jim Langston]

"iwasinnihon" <iw*********@hotmail.comwrote in message
news:11**********************@a34g2000cwb.googlegr oups.com...

>I am writing a simple program to receive over http using windows
sockets. my program does fine receiving text files. But returns the
incorrect data when receiving image files. (The size of the files are
different). My code is below. The header has already been read using
the same Receive() function. What have I done wrong.

ofstream os("file.dat", ios::binary);

//Retrieve the body
try {
while (1) {
l = s.Receive();
if (l.empty()) break;

If found that while receiving binary files it is possible to not receive a
packet during a read, yet the file is still transmitting. In my own code to
receive a binary file via HTTP I don't quit until I reach the file size:

if ( TallyBytesDownloaded >= TotalFileSize )

Since my code is totally different than yours, you probably wouldn't use and
if statement but put it in the while statement.

while ( BytesDownloaded < FileSize )
{
// ...
}

>
os.write(l.c_str(), l.length());

//cout << l;
//length += l.length();
//cout.flush();
}
}
catch (const char* s) {
cerr << s << endl;
}
catch (string s) {
cerr << s << endl;
}
catch (...) {
cerr << "unhandled exception\n";
}
os.close();

string Socket::Receive() {
string ret;
while (1) {
char r;

switch(recv(sock, &r, 1, 0)) {
case 0:
return "";
case -1:
if (errno == EAGAIN)
return ret;
else
return "";
}

ret += r;
if (r == '\n') return ret;

This is a binary file you're downloading, don't expect carrige returns or
line feeds. Just return whatever you received (which is why you may have a
blank packet)

}
}