send( accessing beyond buffer?

I've been working on a game.
One of the things the client-side code has to do is send the name of the player to the server. If I type anything that's more than 3 characters for the name ("Dude" for example), I get error box from Windows saying "Run-Time Check Failure #2 - Stack around the variable 'buf' was corrupted."
I did a little research, and this error only happens when an array is getting accessed outside of it's space.
So my question is, why is send( trying to access beyond 'buf'?

Code:

---

int SockSend(SOCKET *tsock, char* buf, int len)
{
        int nError;

        nError = send(*tsock, buf, len, 0); // Error triggers here; does not stop execution, though
        if(nError == SOCKET_ERROR)
        {
                printf("SockSend: send( failed: %d\n", WSAGetLastError());
                closesocket(*tsock);
                WSACleanup();
                return 0;
        }

        return nError;
}

---

Where 'buf' would contain "S04Dude" and len is 7.

How is buf defined? Does it, in fact, have room for seven characters?

The calling code is

Code:

---

SockSend(&f.psock, tbuf, strlen(tbuf))

---

where tbuf is a char[85].

That seems reasonable. You could check, by printing out before the send call, whether len is correct (if tbuf is not null-terminated, strlen(tbuf) could be just about anything).

tbuf is null-terminated and len is 7.

Is this a full crash? Does data reach the other side? Is it possible that the error message is from the receiver? (If you don't have enough room on the other side, then you would get that message from trashing that piece of memory.)

Ooh, looks like the error was coming from the receiving side. Didn't think of that.
Thanks!