send() call only works for telnet in socket - c++

Question

I am using windows sockets with c++. In the following call I am trying to reply a message to the socket that just connected.
I tried connecting using a dummy client in c++. It would connect but the recv() would not receive anything.
Then I tried using telnet, it worked instantly, just as i wanted.
SOCKET s = accept(ls, (sockaddr*)&clientSin, &s_len);
if (s == INVALID_SOCKET) {
cerr << "Error in accept call: " << WSAGetLastError();
}
else {
cout << "Connection accepted at , socket no. :" << s << endl;
//adding to list of incoming sockets
inactiveList.push_back(s);
//send message to client requesting credentials
char buff[10];
// the character 'x' is a code to the client to provide the server with the credentials
buff[0] = 'x';
buff[1] = '\0';
//send(s, buff, 2, 0);
if (send(s, "From Vic: ", 10, 0) == INVALID_SOCKET)
{
int errorcode = WSAGetLastError();
cerr << "send to client failed: " << errorcode << endl;
closesocket(s);
continue;
}
Sleep(1000);
if (send(s, "From Vic: ", 10, 0) == INVALID_SOCKET)
{
int errorcode = WSAGetLastError();
cerr << "send to client failed: " << errorcode << endl;
closesocket(s);
continue;
}
}
the recv code is:
tnb = 0;
while ((nb = recv(s, &buff[tnb], LINESZ - tnb, 0)) > 0)
{
tnb += nb;
}
/* If there was an error on the read, report it. */
if (nb < 0)
{
printf("recv failed: %d\n", WSAGetLastError());
return 1;
}
if (tnb == 0)
{
printf("Disconnect on recv");
}
/* Make the response NULL terminated and display it. Using C output */
printf("tnb = %d\n", tnb);
buff[tnb] = '\0';
puts(buff);

Answer 1

Taking all my comments and turning it into an answer.
I suspect your recv loop is continuing forever because you haven't sent enough data to make it break out of the loop.
Change this:
while ((nb = recv(s, &buff[tnb], LINESZ - tnb, 0)) > 0)
{
tnb += nb;
}
To this: (notice that I'm allocating +1 for the array buff)
char buff[LINESZ+1]; // +1 for null terminator
buff[0] = '\0';
tnb = 0;
while (tnb < LINESZ)
{
nb = recv(s, &buff[tnb], LINESZ-tnb, 0);
if (nb < 0)
{
printf("Error on socket: %d\n", (int)WSAGetLastError());
break;
}
else if (nb == 0)
{
printf("Remote socket closed\n");
break;
}
printf("Received: %d bytes\n", (int)nb);
tnb += nb;
buff[tnb] = '\0'; // null terminate the end of the buffer so it will print reliably
}