C++ client needs to find out socket was closed by twisted server - c++

Question

I have a twisted server that does something and then closes the connection. The python clients understand with
clientConnectionLost(self, connector, reason)
that the connection was closed and that works fine.
However, I also have a C++ client communicating with the same twisted server. It currently doesn't seem to understand that the connection/socket was closed. How do I check for this?
string tcp_client::receive(int size=1024)
{
char buffer[size];
string reply;
int msg = recv(sock , buffer , sizeof(buffer) , 0);
// Receive a reply from the server
if(msg < 0)
{
puts("recv failed");
// Exit the programm
exit(0);
}
reply = buffer;
return reply;
}
is the C++ client's receive code.
How do I reach the same/similar functionality of clientConnectionLost with the C++ client?

Answer 1

From man recv:
The return value will be 0 when the peer has performed an orderly shutdown.
So after recv call, you can write:
string tcp_client::receive(int size=1024)
{
char buffer[size];
string reply;
// Receive a reply from the server
int msg = recv(sock , buffer , sizeof(buffer) , 0);
if(msg < 0)
{
puts("recv failed");
// Exit the programm
exit(0);
}
else if (0 == msg)
{
// the connexion has been closed by server
puts("Connexion lost!");
// close the socket
close(sock);
// return something
return string("");
}
reply = buffer;
return reply;
}