recv() returns always 0 - c++

Question

I've a problem with recv() function that I can't explain: it always returns 0. I've a client/server application in which the server simply has to receive a string from the client through the internet (different pc). There are no connectivity problems, and I also tried to send a string from server to client: it worked.
I search in the blog and what I found, recv() socket function returning data with length as 0, non-blocking recv returns 0 when disconnected, Recv returning zero incorrectly, didn't help me to understand.
Here I post the Network class:
Network.h
class Network
{
WSADATA wsaData;
WORD wVersionRequested;
int Port;
unsigned int byteReceived, byteSent;
SOCKET listeningSocket, connectedSocket;
SOCKADDR_IN serverAddr, senderInfo, clientAddr;
int caddrlen;
char buff[DIM];
string buffer;
public:
Network();
~Network();
void Recv();
};
Network.c
void Network::Recv() {
int n = recv(connectedSocket, buff, strlen(buff), 0);
setByteReceived(n);
buffer.assign(buff, n);
cout << "Buffer is: " << buff << endl;
if (byteReceived == 0)
cout << "\tConnection closed" << endl;
else if (byteReceived > 0) {
cout << "\tByte received: " << byteReceived << endl;
cout << getBuffer() << endl;
}
else {
myFormatMessage(WSAGetLastError());
}
}
The behaviour in the end is the following: client and server are connected, the server returns 0 from recv(). I tried also to run both programs on the same machine. Thank you for your help.

Answer 1

You have:
void Network::Recv() {
int n = recv(connectedSocket, buff, strlen(buff), 0);
...
If strlen(buff) returns 0 (because buff contains a null byte at index 0), you will be asking recv() to read 0 bytes, so it will return 0 bytes. You should be using sizeof(buff) instead of strlen(buff).