In findClient() in TFTPServer/main.cpp
the session time out determination is suspect.
I think it should be more like:

	DWORD dwExpiration = g_Clients[i].dwLastSignOfLife + TFTP_SESSION_TIMEOUT;
	if (    g_Clients[i].eOpcode 
		 && (g_Clients[i].dwLastSignOfLife < dwNow)

// && (g_Clients[i].dwLastSignOfLife < dwExpiration) //error?
&& (dwNow >= dwExpiration) //better, since 'now' has hit the expiration time?
)
{